As mentioned two weeks ago I went on a business trip to Florida and decided to mapblog the trip using GPS and Cellphone. Here's the entire cellphone mapping article, the resulting trip maps, and the cell mapping summary.
It worked great! The first two days of the trip I didn't have computer access and couldn't check up on how things were working. I was relieved to finally see the maps and all of the messages were getting through.
I didn't track the trip coming back, mostly because I thought we'd be taking the same route (we didn't). There's some thoughts about future features and also a mention of remote SMS weather monitoring on the SMS Fun page.