Here is how I APRS.
Using APRSDroid on a cheap cellphone designated for the South American market ($40 from Amazon) and the accessory cables supplied, I hacked together something that works quite well.
The small 3.3uF cap block the microphone bias voltage from the phone, and the 5K resistor tricks the phone into thinking there is a headset attached. My only issue is the cable is quite small, which makes it easy to damage.
See my other post on APRS HERE.