Garmin is based here in the KC area (Olathe, Kansas), so I'm always happy to see their name mentioned.
The Rino 110 weighs 7.6 ounces and will run the GPS and radio for 14 hours on 3 AA batteries. You could substitute Li-Po for the alkaline batteries and cut the weight by 2 ounces. The spec sheet says it's 2.3" wide by 1.7" deep. You'd probably want a 3" body tube to leave room for some padding. I'd want to beef up the battery holder (or go with external, soldered battery connections) to prevent loss of power at launch due to batteries compressing their little springs. Otherwise, the thing looks like it's built like a tank.
As mentioned, you would need an external circuit to key the Push-To-Talk function via the external microphone jack. It sends its location when the button is released, so a timer that closed a reed relay for a second then released for thirty seconds would do fine. You can only send position reports every 30 seconds (FCC rule), so using this for real-time flight profiling is out. The Rino DOES store the track internally, so you download the profile after you've recovered the unit.
The tracking radio stores the last received fix, so even if the radio does not survive the touchdown, you'll have some idea where it's at.
Garmin just updated the firmware so that position can be reported on GMRS frequencies instead of only on FRS. This will double the tracking range. You DO have a GMRS license, don't you?
Hope this doesn't sound like I have experience with these little jewels. I'm just perusing the docs on Garmin's site. Gotta cheer for the hometown team!
Oh yeah, these are going for around $145 each.
Rick
WØYGH