Pair of 3DR radio knockoffs from RCTimer = $40
Pair of Arduino Pro from Karlsson Robotis = $30
MS5611 breakout from Ebay = $20
Some homebrew speaker/amplifier = $10
That is $100 (plus shipping)
I think the cheapest route would be is you have a newer radio with telemetry. Then you could just put together a vario (Arduino + MS5611) that would transmit back through the telemetry system. Not sure if that would support audio though.
Easy is in the eye of the beholder.
Thank you for your answer :)
It should be possible for me to actually do this :)
I think I'll give it a try, but I still want to hear about any ready-to.fly products :)
I am the founder of Flyte Park (www.flytepark.com). We have a couple audio variometers that offer a good value. We designed them for hang glider and paraglider pilots, but some of our customers are using them in RC planes too.
They have a high resolution pressure sensor and sound great. They start at $99.99 for our simple model (Microvario) and $179.99 for the more advanced (Pro) model. There are some GPIO pins exposed on the PCB on both models, so this might be helpful on your projecdt too. If you have any questions, don't hesitate to ask.