plenty of bluetooth products that mount to steering wheel and can control media (play/pause/next track/etc.) and answer/end calls. they all use a standard bluetooth interface so they should work with any phone. examples:
with one of the larger ones that have numeric keypads (like this...), you might could use an app like Tasker to make some of those extra buttons do other things (instead of just being a dial-pad).
there are several car home screen type apps in the play store... but why? you can customize the android desktop endlessly - just make a desktop screen with whatever app shortcuts you want. you can get a custom launcher like Nova and then you can set the size/spacing and more. most launchers will also let you "lock" the desktop - so you don't accidentally move or delete things when trying to use the touch screen in a moving car. you can of course have widgets too... the Torque OBD app will let you put float pretty much any gauge outside the app, and there are other plugins for it that give you specific widgets for the desktop. and finally, you can get an icon pack to go with the launcher so your UI looks consistent.
for example, here's an older version of my vehicle tablet's desktop:
if you definitely want a dedicated car app, search "car home" on the play store...