I've sent an SMS over the APRS gateway using nothing but a cheap handheld radio and the APRSdroid app. The app can emit audible data chirps, so you just compose

I've sent an SMS over the APRS gateway using nothing but a cheap handheld radio and the APRSdroid app. The app can emit audible data chirps, so you just compose your APRS message, hold your phone near the radio, and push the PTT button. Not very practical, but there's no custom hardware or connector required!