Brix Meter (refractometer)

Has anyone used a brix meter as part of their grow?

Also known a refractometer (or reflectometer?) , a brix meter measures the sugar content of plant tissue. It has a prism on one end and an eyepiece on the other. When a drop of sap or juice is viewed through the meter a reading is given that indicates dissolved solids in the plant's system. This can give a much better picture of plant health than guesswork based on how the foliage looks etc. as well as alerting the grower to deficiencies or toxicities in the soil/medium/water.
I think they can also be used to assess ripeness, as I originally heard of them in the context of wine-making (although perhaps sugar levels can't be used to gauge ripeness in Cannabis as it is in grape vines.)

The meter isn't terribly expensive, around $100 for a Milwaukee.

Has anyone had any experience with these?

A couple links:

Brix - Wikipedia, the free encyclopedia

The Brix Meter explained - General Hydroponics - Indoor Hydroponic Gardening, Hobby Gardening, Hydroponics System and Hydroponics Experiments

http://www.extech.com/instrument/pro...RF10_15_UM.pdf
[Instruction manual for an extech brix meter, shows the usage procedure and the kind of data collected.]

The Growing Edge Magazine - Gadgets and Gear for Hi-Tech Hydroponics
[this is a crazy article that will make you wish you could print money. The brix meters are mentioned towards the end.]

Marijuana Growing: Indoor Gardening : Recent Innovations in Growroom Technology
Cervantes article, mentions Brix meters.

Brix Refractometer - Hydroponics Forum - GardenWeb
[random forum discussion of brix meters]

yeah brix meters are useful when making sure u plants are healthy
a brix reading of 12 means plants are healthy i think it is ill look it up and get back to you on that one
a good investment but not very neccesary a ph meter and a ec/ppm meter deffinately more important but if you got the money get it =)