This is actually one of the few reasons I wouldn't be totally against this kind of technology. (For security reasons, I think that putting software with open on the air connections into a 1-2+ ton metal machine powered by explosions that moves ridiculously fast is mostly a bad idea.) Particularly in America, even fairly 'bicycle friendly' cities can be pretty dangerous to ride a bike in, and often for design reasons that force bikers to either endanger themselves or put themselves in a place where cars will make dangerous maneuvers near them. (Example below) A system that you could attach to a bike that would basically give your bike a warning system for nearby cars (and them a warning system for bikes) would be fantastic. Another good thing about it would be that it could be used to give motorcycles the profile of a car, which would make riding them much less dangerous: no matter how safe a motorcycle rider you are, you're smaller than a car and that lower visibility can cause accidents.

The promised example: A common dangerous design for bikers in cities is bike lanes right up against a lane of parked cars. Depending on how fast a biker is going and the local terrain, someone opening up their door into the bike lane can be lethal: you might not have time to stop yourself, and your options might be to slam into the door and maybe a person getting out of the car or to swerve into traffic, both of which are very dangerous. The safest thing to do when that's the case is actually to ride in the car lane, but that has its own dangers: many cars will try to pass you by going part of the way or all of the way into the lane to the left of them, which might have oncoming traffic or traffic coming from behind that the drivers don't check for, which can lead to them swerving back towards you. That means that the most safe thing you can do for everyone in that situation is to ride dead center of the lane so that passing you by going only halfway into a lane isn't possible (since many car drivers seem to treat that kind of passing differently from an actual lane change), but car drivers absolutely hate that and will do all sorts of other dangerous things like following super close.