After enjoying the blessing of HDMI-CEC also known as Sony Bravia Sync (other vendors have other names). I wanted my media center pc to have the same functionality. After a lot of googling I came across this USB-CEC adapter by pulse-eight in UK. Around Christmas I ordered one and are so far very happy with it. I highly recommend it togheter with their special build of openelec that is XBMC "in a box". Installation takes 10 min and then your running.
That is the way I like it !
The downside is that I havent yet managed to get it to boot the XBMC computer from the HDMI-CEC commands from TV. So I still have to use my phone to wake it over lan. But this is supposed to work from pulse-eights latests release so probably I just have to fiddle with some USB settings on my computer. Just need to find time.
http://www.pulse-eight.com - I like!