Hi, Chad: don't know if there are any GPS apps for the G1, but I think you'd find that the accuracy is suspect, say +/- 5 - 10 meters because virtually every phone on the market doesn't have the accuracy needed for golf.
Here's some more info:
http://www.oobgolf.com/forums/viewtopic.php?t=1143
p.s. I recently golfed with a buddy who had a Skycaddie (the company that manually walks every course). We came up to the 10th hole and both drives finished about 2 yards apart. The pin was in the middle, and I lasered it at 178 yds. He had 193 to the center on his Skycaddie. We both said, "Whoa!" and wondered what was up.
I hit my shot and then 30 seconds later his Skycaddie reading changed from 193 to 175. We then noticed that we were standing under a big oak tree. We're guessing that the Skycaddie didn't have a fix on enough satellites initially, but after 2 minutes it was able to pinpoint the location.
So if you do get a GPS it might be good to get one that shows on the screen the # of satellites it has locked in. That will give you a better sense of your level of accuracy (and also letting the GPS settle down after you stop moving can also help).