I want to see how high my plane is going. Is there an onboard altimeter that I can get that would work in an rc airplane? All it needs to do is record the highest altitude. I guess I can have someone record the distance and angle and then figure out the
height.

"How high"
http://wingedshadow.com/

Yep, I've used both the How High and How Fast meters. They work great.

Note unless they changed something in them. If you power the meter off your rx, don't power down the rx or you will loose your info on the meter.

thats pretty cool. I may consider trying "How High".