Take it with you. I used my Nexus One with GPS on my DTW-LAS flight this week. I admit I was a bit worried about a chicken little freaking out that I was holding an electronic device against the window. Nobody noticed either way.
Note, the N1 sucks at getting a GPS lock in flight. My Garmin Nuvi is much better. It is faster on the ground though, I assume because of the use of phone towers to narrow down the rough location.