For those with Mercedes Benz vehicles, recently I had my car serviced and was offered a free Mercedes Me Bluetooth Adapter. For info my car (W205 class MY14 build) is 5 years old and out of warranty.
This is a plugin device that goes into your OBDII port and communicates with your phone via bluetooth. Pretty nifty since it picks up all the fuel consumption, speed, location and puts it all in an App (android/IOS)
Doesnt have the full blown features like remote start etc, but its nice for the tech enthusiast.
You will need to create an account on your Mercedes-Benz.com.au and link your vehicle details. The module is apparently free from your local mercedes dealer. With rego and app setup etc it took around 15 mins to setup overall.
Mate had a 2013 B Class and also got this for free after contacting the dealer.
p.s. You will need to have a high yield investment to get this