Remotely Possible is a iPhone/iPod Touch that lets you control your Windows based computer including your HTPC. The app is $2.99 but seems like a really good deal for what it does. It can detect your Windows based computers on the network and auto-connect to them. It allows you to launch apps like Windows Media Center and Hulu. From there you can control it with gestures or buttons you customize. If you have tried it out let me know.