For the love of everything that is holy I have been trying to find this solution for so long...
I'm basically looking for an Android compatible version of something like the Kensington LiquidAUX setup. For older cars that don't have built in bluetooth but DO have an auxillary in cable, this solution lets you plug the aux in cable into a bluetooth receiver
and also gives you
a remote that attaches to your steering wheel that can change music tracks. You can see what I mean from these pictures:
I have been searching and searching and searching and have never found anything that will accomplish this with an Android phone. I had privately always wondered if a Pebble watch could achieve this.
Ran across this old thread randomly while reading about the Pebble, I know it's blatant necromancy but I felt compelled to post and mention that Kensington made a standard Android compatible version of that device, same name and everything. Only difference is that instead of having the 20 pin cable sticking out it has a USB port down there that will charge any old phone...
The thing is old as dirt and it's actually discontinued I think so good luck finding it, wasn't even meant for Android per se, I've been using mine for the better part of three years! Worked fine with my last dumb phone (a Sony Ericsson) as well as my last three Android phones. The only occasional issue is that it'll lose power if wiggled but that could just be the fault of my 2007 Civic's janky 12V port (never bothered to try it in another car). The brilliant part about this thing is really that wireless remote, I didn't even use that wheel bracelet it comes with, just Velcro'd it to a slot on my Civic's steering wheel and it damn near looks stock. I've no idea what kinda wireless protocol they use or whether it communicates with the phone or directly with the base, I'm pretty sure it's the latter...
There's lots of Bluetooth devices like this one meant to sit in the dash or discretely below it, some might even be better suited if your aux jack and 12V port aren't immediately adjacent (I've seen smaller devices) or if they're pretty hidden (the mic on the LiquidAux isn't great), but I've NEVER seen one with a wireless remote like this (they often don't even have any kinda music playback controls)... And I've looked around occasionally too cause I've got several friends with semi recent 2009-2011 cars without BT built in for whom this would be an awesome gift (plus I'd kinda like a backup, I'm gonna be stuck with my Civic for a few more years still!).
If anyone knows of an alternative I'm all ears, I guess something like the Pebble (not necessarily a $150 smartwatch) that can control playback while another device handles BT streaming would sorta work but it seems like a workaround... I've no idea why Kensington stopped making this thing, it was kinda ahead of it's time IMO since piping music over BT wasn't anywhere near as common or popular when it came out, Android was barely catching on and iOS BT support lagged dumb phones...
In fact I remember being mildly annoyed that my Sony Ericsson dumb phone fully supported the playback controls on the remote yet iOS on my IPod touch (2nd gen) only allowed play/pause but no track skipping (things like that soured me on iOS, that was the one and only Apple device I owned, tho I'm glad to have tried it out). There's tons of BT-less cars on the road for which this would be a perfect solution. Someone oughta petition Kensington to bring it back or put out a rip off thru Kickstarter... I remember paying like $45 for it during a CompUSA sale (before they first closed, yes it's really that old, pretty sure it preceded the iOS version), beats the heck out of replacing your stereo deck just for BT IMO.