I have a couple of Radio Shack digitraveler GPS's to play with also that I wanted to put a serial cable on it to have a cheap GPS for field measuring and could leave it on the ATV without worrying about it getting damaged - have not gotten around to get them fixed up either.  Need to start on them sometime.  Maybe after harvest.  Could even be next years harvest.

I really do like using Guidemate.  Screen size works fine for me.  Works nice to set up a job and get all my field recordkeeping done on one step - mainly when spraying.