On Friday, July 27, 2018 at 4:21:41 AM UTC-4, Charlie Quebec wrote:
I use a cheap android phone with xcsoar, kept in the side pocket, fully charged. Powered off it can be going in a minute, and using its own GPS.
I have a mechanical Winter as vario backup. You dont get to go solo here without the ability to do a circuit and land with all instruments covered.
Losing power would little to no inconvenience.
A truly independent backup that costs less than $100.

I have a mechanical variometer and a chart. They have gotten me home when needed for more than 40 years. I expect they would again albeit without a flight log.
That said the only power issue I've had was due to a very low primary battery and a backup that wasn't charged as I thought. I turned everything off except the ClearNav and got around OK.
FWIW
UH