I had him check digikey.com for a cheap altimeter, and we found one for $7, but the lead time was too long. He's moving pretty soon, so we needed an immediate solution. I decided that we could use an accelerometer, and when it reads 0-Gs on the vertical axis, we'd know it was free-falling. (or had ended acceleration)
We set up a timer that would deploy the parachute a given time after the acceleration ends.
Here's the underside of the board. I drew it up in EAGLE and etched it in the shop at work. You can see it's a little on the hablich side, needs a dose of alcohol and it could also use a small redesign. I noticed after I got the software running that a couple of the outputs were configured wrong in the hardware. If I ever make a V2.0, it'll be a little more attractive.
The red and blue wires arm the device. These get twisted together after you get the rocket set up. so it won't go off unexpectedly. The device also monitors the nichrome ignition wires. If one of the wires gets broken, you can tell from the LED indicators on the bottom.
Hopefully we'll be able to test it out next week after I get back from Mexico.