this should work on pretty much any Android device but I'm posting it here as it is the only one I can/have tested it on.
I cannot post links yet but it can be found on Amazon UK under the name "Satechi BT MediaRemote Bluetooth Multi-Media Remote Control"
It's a small Bluetooth remote for iPad/iPhone/Mac and very quietly mentions Android so I decided to buy one and see how it goes as I needed something like it for my car.
Anyway it arrived this morning and I love it, I've successfully used it and I've been able to remap keys using the "External Keyboard Helper Pro" app by "Apedroid" which allows remapping of keys to media keys or launching apps.
All keys on the remote can be remapped except the wireless symbol which un-pairs and goes into discover mode.
My requirements were a remote that allows me to change tracks while driving but it also got Google now working in my car Bluetooth system. (it did not connect properly when I launched it via car voice controls)
I have now got the keyboard button remapped to switch to the maps app and the mute button to launch Google now so once Google now is done I have a button to go back to the navigation screen .
I have also been fairly successful in getting this to work with Tasker however it required a small workaround by exporting the task as an app (via Tasker App Factory) and then using "External Keyboard Helper Pro" to launch it.
My only issue with the remote at the moment is that it connects as a hardware keyboard meaning I cannot type while using it (obviously not an issue in the car though)
All this was done on a non rooted Nexus 4 on 4.4.2 so root is not required by the way.
If anyone has any questions feel free to ask, I'm going to figure out how I can bind the other 9 keys on the remote
Oh and finally if you do use the app in question and use Tasker I'd recommend exporting a Tasker task which launches the intent "android.intent.action.VOICE_COMMAND" rather than using the built in voice control key setting.