This has been discussed a few times recently. You're only option for a US spec LC is a GROM Vline (Lexus Toyota 2006-2009 GROM VLine Infotainment System Upgrade Video Interface). It doesn't replace the head unit but does provide an android powered system that interfaces with the existing touch screen. It's rather beta at the moment.
I like this solution. Only problem is, your phone will have to be a hotspot. With AT&T, they won't allow tethering with an unlimited data plan.