On Aug 29, 3:09*pm, Tony wrote:
I know you don't sell LX vario's anymore Paul but the LX16-D has a
built in flight timer function and is a nice little audio vario to
boot. *I put an LX16 in the Cherokee this season and have enjoyedit so
far.

http://www.lxavionics.co.uk/variometers.htm

another possible solution, and actually more in line with the original
question and price range, would be to work out some sort of weight on
wheels switch on the glider to run to the Hobbs meter linked.