For tracklogging, I’ve recently starting using two devices simultaneously: my trusty Garmin eTrex Vista HCx, and my phone (HTC Dream a.k.a. T-Mobile G1, the very first Android phone). Originally, I was just trying to see how accurate the phone’s GPS was (pretty good, actually). Then I realized that if I got two recordings of the same track, and they agreed, I could trust them more. OTOH, if the two tracklogs don’t agree in a significant way, they’re probably both wrong. (This happened to me last week. I don’t know if it was because of heavy cloud cover, or bad alignment of satellites, or what, but I do know I have to go back and try again.)

This obviously works best when I’m walking, with both devices side-by-side in the palm of my hand. Not so good when I’m riding the horse, where I have the Garmin clipped to my belt, and phone in my pocket.