I have an idea for an accessory, but I doubt it will ever be made
I would like to see an accessory that would allow me to use an iPhone as a universal remote. The accessory would have to consist of software and hardware. To be successful, I think it would have to come from Apple vs. a 3rd party.
The hardware end would consist of a small box with an IR transmitter in it. It would also have to include a Bluetooth chip. The iPhone could then communicate with it via Bluetooth and the device would then send an IR signal to the TV, stereo, etc. Since it would use Bluetooth the iPhone need only be within 30 feet of the device to use it and wouldn't have to be pointed in a specific direction like most remotes.
IMO, the software is the tricky part. It has to be able to be customized to individual needs but remain easy to use. This is primarily why I think Apple would have to develop it. Since I am probably the only one that would buy this accessory, I doubt Apple will spend the time and effort to create it