Lots 'o home theater companies are creating iPhone apps to control their own company's components, but what do you do when your TV is a Panasonic, your Blu-ray player an LG, your receiver a Denon and you have a Roku media server and a Motorola cable box?
Get the Gear4 UnityRemote.
UnityRemote starts with a mini-muffin sized RF device that you simply place somewhere where its emitter can "see" your component stack. It's a 360-degree emitter, so no pointing necessary. You download the UnityRemote iPhone/iPad/iPod Touch app, tell it what components you have, and your iPhone is now a universal remote. Better - you can wave it around the change the volume and channels. It retails for $100.
The mini-muffin RF thingie runs for around five-six months on three AA batteries - and it actually comes with three lithium ion cells (alkalines will have to replaced sooner).
Of course, if you take your iPhone with you, whomever is left at home will have to use their multiple old-fashioned remotes.