Cheap is relative. You have lots of options. I'll start with easy ones...
Buy a new Ford product with Microsoft Sync. Bluetooth, iPhone integration, voice selection for music and dialing, yada yada yada. Cost: $16-70,000; employee pricing at Ford is still active, and its a great deal. They actually give you real employee pricing too, unlike GM, which gives you crap.
Various units under $300 offer a din-sized ipod connectivity (may require additional hardware) and built in bluetooth phone connectivity. Sony MEX-BT2600, Eclipse CD3200, Pioneer DEH-P7000BT or FEH-P8000BT. Most Alpine headunits will accept iPod and bluetooth adapters. I recommend either of the Pioneer units I mentioned, though, due to ease of use.