You can retrofit any FM radio with a plugin unit for under $50.
http://www.amazon.com/iSimple-IS31-Antenna-Modulator-Aftermarket/dp/B002U5XPBE/ref=pd_sim_sbs_422_1?ie=UTF8&refRID=17789FX95116ZY5AH26J
Most 2015 cars still do not have bluetooth or Aux built-in. Very few built prior to 2010 have them. You may get lucky and find a few starting in 2006-2007, but you will be severely disappointed if you expect it in any vehicle. They have been a very popular addition and cause for factory stereos to be upgraded, especially by the younger generation, just learning to drive within the past few years.