I use my N900 in host mode to connect using the amazing RTL-SDR $12 software defined radio USB dongle. The dongle and wire antenna fit on my keychain and I can listen to air traffic control while I wait in the FBO for my rental airplane to be prepared.
I am looking forward to ADSB(dump1090) to be compiled so I can watch the radar transponder tracking of nearby aircraft so I can see if friends are in the air.
The N900 is what happens when a major phone corporation orphans a development project and they end up making insanely awesome phones for tech savvy end users rather than building dumbed down money pits to be exploited by phone companies.