hi pull up now, which one are you referring to?
the one i am referring to is the Spektrum telemetry module.
with this, you need to monitor either using a telemetry ready transmitter, or in my case, you need to purchase an STi interface which attaches to the bottom of your iphone, or i pad, or i pod.
you can attach an ear piece to your i phone, ipad, or ipod, i would prefer to use the one from apple, since it came with my phone, and thus, is one less expense.
then, you can program it to tell you the voltage, rpm, speed, altitude, etc..
with regards to altitude, you are correct, it will tell you once you get over a certain altitude, but now low, i will have to look into that.
now, my system will give the voltage of my "flight pack", which for me, using a gas motor with an ignition battery, that is where it is plugged in. my second reading is from my receiver battery. the monitor will read the actual voltage it sees. for the ignition battery, i have welded a deans plug to the lead that connects to the telemetry module. the deans plug then attaches to the deans on the Life A123 battery i am using for ignition. the battery has 3 leads coming out of it, 2 are futaba type, and one is a deans. then, i have programmed the iphone app to set battery high voltage, low voltage, and high charge. now when i look at the monitor, it will say full charge if the voltage is 6.6 volts. as battery volts decrease, once it reaches a threshold, it will sound an alarm, i have set this for 6.0 volts. also, i have programmed the module to say out all of the parameters on 30 seconds intervals, automatically.
there is so much more to this, i can go on and on, and it takes a lot of tinkering with and reading about it to understand it.