The Foretrex 101 does interface, though you have to buy the cable. Some of the reasons I was considering the F101 rather than the Geko or eTrex series are the specs from Garmin's web site and other places. Specifically, the F101 is listed with specs similar to the Geko 201, but costs less and has better battery life (probably because it's a slightly newer design). The eTrex units, are twice the weight, although you do get AA batteries rather than AAA, but the base model eTrex, which is the only one that can compete with the F101 on price, doesn't have things like the Celestial Info Page, which might be useful as long as I'm getting a GPS.

So, I'm pretty well decided on the Foretrex, I just wonder how well the thing actually does its main job.