Not sure what programs are offered on SXM. You can rent cell phones or buy a cheap one at either of the Island's mobile providers or authorized distributors:
LIME:
http://www.time4lime.com/ky/DigiCel:
http://www.digicelcayman.com/ LIME has a "phone in a box" that is around $50 US and comes with pre-paid minutes and is popular with tourists. You can add minutes at stores all around the island.