It's a special RF remote. It works directly with the dock. It is rather short range too, likely because it uses a button cell battery. On the plus side, the dock enables USB host, allowing for use of flash drives, keyboards and mice.
I got mine for $55 on ebay. Keep in mind that it doesn't come with the hdmi cable(I know), but you can get one from amazon for like $5.
[Edit] It looks like I was wrong. It is IR. Just checked it with my camera app. Most camera sensors detect IR and translate it into white light.
Sent from my DROID BIONIC using xda premium
Current Phone: Droid Bionic with 16GB card.