Theres an app called carista that does all this. needle sweeps, horns,lights etcit works from a Bluetooth dongle but don't get the cheap one like I did. spend at least a 10er otherwise it wont work
yeah that's the one. its free to download but they charge you for each tweet. like needle sweeps would be 2quid etc.I brought the cheapest dongle I could find (3 quid I think) As a result it doesn't work witrh carista but it works perfectly with torque app Pro.
He wants to be able to sound the horn or make the indicators go off remotely rather than code them inYou would need aftermarket 3rd party unit.