Ahh so you want outdoors. You have some good base ideas. If you want to have 5 plants outside that you have hooked up so you dont have to visit them more than maybe 3 times during the season to plant, then culling males and switching to flowering nutes and finally harvest then it shouldnt be too hard to do. If you're serious and not just having those "high time" dreams of having fields full of nice busy females like we all have then with a little work you can do this no problem. But making something automated like this means you are going to have a location that is close to water and isnt to close to anyone so its going to be even harder. You will have to build a few different basic systems and put probably 50+hours outdoors once you find your spot just to start setting it up and get it perfect which it probably wont be till you have a few grows using the system. I also dont know if you're doing this outside your backyard and you can hook it up close to you or if its 50miles+ away.
Water/nutes/space:
Well i would find your spot and build a little tree fort up above in the nearest biggest and tallest tree have it 30feet up or so i would say you will need a water source somewhere nearby. It doesnt have to be anything fancy but it should be enough to support your weight+100pounds. I would use water cooler bottles (5gallons i think) for your nutes and water, 1 for your nutrients and 2 or 3 (depending on how you set it up) for straight water along with two valves some big water pumps depending on distance to your water source and how high up your plants are and a couple hundred feet of drip line's(need to find out distances), motors to move the valves for water/nutes and a few car battery's and solar panels.
http://www.livingwatercanada.com/imgs/5gallon.jpg
Youll want to put your 5gallon waterjugs or whatever you use strapped against the tree but upside down (How they sit on the top of a cooler), i would use some type of rachet strapping for each one and have it go through handle to keep it against the tree, each jug should have its own strap through the handle to make sure they are all nice and tight and then one big strap all around the tree and outside of the jugs just to make it a bit tighter. Keep all three on the side of the tree trunk that your treefort is in (Dont be stupid and put one water res on the other side of the tree) at the opening in each bottle put your valves there, i would just use the same type they have for washing machines along with a small chain hooked up to a motor to spin it. For nutes i would dilute them down a bit depending on what type you get along with a smaller hose that leads into your main water res. You want it so that 2-3seconds of your nutrients is enough for one feeding but not to much. To figure out how much in a feeding get a PPM meter and get some of the water you will be using along with your nutrients and find out how many ML(or however you want to measure) it takes to bring your PPM up to 750 or whatever level is suitable for you to a gallon of water, then run your hose for a second(or 10) to find out how much nutrients flow in that time period. So if lets say it takes 20seconds to get enough nutes to bring your PPM to 750 for a gallon of water, then you have 5 gallons youll need to run it for 100 seconds(obviously you will be looking at running it for a lot less time).
You will want to have a decent sized water pump depending on distances. Get one of those big plastic buckets they use for paint (they use them for hydro a lot) and get a few different sizes of mesh screen, cut holes in the bucket and place your screen in (keeping the bucket sturdy but having enough mesh holes to allow large amounts of water to flow freely. You want to allow as much water into the bucket without getting a lot of dirt/things that can block it up. So play around with a few different sized screens to find out. Fill the bottom of your bucket with cement or something heavy and stable to keep it weighted down, submerge your pump into your bucket and put the bucket deep in your water source. Probably going to have to make your wire from your pump to the power source on land longer and well sealed from water so plan on having 20-30feet of extra sealed wire. I would look into some type of large metal screen thats solid and you could put overtop of your bucket just to protect it from passing objects and knocking it over in your river/pond. On shore you will need a battery source like a car battery that can be recharged by solar panels or something like that and a few power inverters i am guessing, it really shouldnt be to hard to do. From the waterpump you should weight down your hose and have it come to shore buried a few inches down going towards your treefort. For stealth i would keep everything buried a inch or below and also stop animals from discovering it. Your water line goes up the tree trunk and into the top of your water res where its stored till the valves dump the water. Hoses/pumps you will probably need to take some figuring out, you need to have a small enough line to keep the water pressure up and a big enough pump to get it the distance while not pumping out more water then your bucket can hold (small worry really). You wont need to have it pump all the time so if it takes 5hours to slowly fill your water res's then thats no big deal as long as your battery can run it and recharge in time.
From your water res i would have some 1/2" or 1" drip line irrigation running to your plants with 1gph drip's or something like that, the great thing about this is that you dont need to have the tree fort far from your plants. Using the battery/solar panels to run your motors to turn the flow on and off to the plants. This can all be run on timers if you wanted so that once every 2-3 days your water pumps to the tree fort then 12hours later or however long you want the water is then to the plants and having your nutrients being added whenever you need them. You could run the lines from your water pump straight to your plants but i like the idea of having a place to store it and monitor it while you can also mix nutrients into it. Using subcool's super soil so you dont have to add nutrients and just having the water straight to the plants is the easiest way. Drippers can be skipped but i would worry about having all of my water flow out of the first few and never getting the last few the amount of water they need, mind you having it straight from the pump might cause to much pressure on the drippers but i have no experience with that
Getting it up to this point and having it flawless so it doesnt need to be monitored is very possible and shouldnt cost to much money wise as most parts could be found second hand. Its just going to involve a lot of work and getting your timers and making sure everything runs without you needing to be there.
Computer/webcams: From here it gets more difficult. You will have to do some research and testing to find out how long you can run a computer from a car battery using solar pannels to charge it. It shouldnt be to hard to have it stay in sleep mode and flip on when you need it so its not hogging all the power 24/7 but watch out for some basic problems like having a battery that is meant to work for a few hours and charge rather than always having a constant small power draw from it like you would with a computer in hibernate. Use a phone to "teather" to your computer with USB so you can use the internet or pick up a internet stick that plugs into the USB that most cellular places have (costs a couple hundred bucks along with monthly fee's). You can hook all your webcams up but they probably wont run while in sleep mode and you would need a huge harddrive to back it all up when really if your webcams don't turn on you know its been busted. You could set up some digital cameras with motion senors so if someone comes near it takes a picture and you can download those pictures by having it plugged into your computer with some long usb cords.
Hope it helps somewhat.
I would remove the gigantic arm and design it in a way were it could be internal until needed shouldnt be too hard...
now with this done all the rest is just accessories (water res., nute dispenser, add some garden snips, and solar panels ) 
we have good summers her its humid as shit but its always like 80-90 degrees and it rains enough but even if we go a week without a good rain i got plans for this bot to carry 4 one quart gatorade bottles or somethin similar and ill have probably 5-10 plants in a zone and have maybe 5 to 10 zones all along staying close to a water source and vegetation should be around 4-5ft high around the immediate area around plants. with each plant seperate in a random pattern across maybe 50 yard zone... and each zone could be maybe 50 yards apart... then one might say its plausible to be able to go to creek or lake suck up a gallon of water thru active carbon filter passes thru a one way valve into bottles...
