Thanks, I'll check that out, makes sense that screen on would kill battery, guess I didn't full think it through. I actually used my car nuvi garmin last year, just for tracking route/speed/etc - if I put the screen brightness at 0 (un-viewable), it would last about 6.5 hours - just a bit shy of my overall clarksville century last fall (first 100 for me). Of course, some riders joked about me riding with a laptop on my handlebars, but it worked....
According to Ride with GPS there is an APP called Velodroid that will do what you are looking for. I checked the market and there is a free and pay version. Not sure if it will do the trick. About all I know on this one because I use a Garmin 705 on my rides.