I'm not sure why people think that an app can replace hardware. Does your car have some sort of interface that allows for an app to unlock your car doors (this is what Viper SmartStart does)? If not you need to start there.
Similarly, apps can't:
1. Make your device replace infrared remotes to contol your audio video equipment (no IR emitter).
2. Enable your device to receive OTA TV signals (no tuner).
The list goes on and on. Just think for a moment and consider the chain of software and/or hardware needed to enable the functionality that you're asking about. What does your device include in its feature set? Does it have what it needs to accomplish what you're looking for? There are many apps that also require a service to enable their functionality (again, Viper SmartStart falls into this category as well as Schlage's solution and even Google Voice, among others).