I have the Slingbox Pro and love it. Only one person can log into any Slingbox model at one time.
I like it because any PC can view the multiple inputs of my Slingbox. This includes a "raw" cable input, Microsoft Media Center PC input, and another Aux input that I may put a camera on.
I can also view this on my phone and love doing so while waiting in airports, doctors offices, etc...
All you need is the client software loaded on your PC's and mobile device (there is a one-time fee for downloading the mobile viewer). You select what kind of input is attached so the proper "remote" can be displayed on the client (for instance I have a replica of an MCE remote displayed on the screen when selecting the Media Center PC's input to watch).
Another HA use that Cocooner
Skibum is doing is viewing his (security) cameras via the Slingbox. He also interfaces the IR output to his Ocelot, which then selects which camera he wants to view (he promises a How-To on this in the future as it sounds like a really cool application

)!
One more use I thought of is to get this as a "gift" for my brother who lives near Pittsburgh (he has cable TV and broadband Internet access) so I can then watch all the Steeler games during the NFL season without having to pay for any cable TV "season passes"!
There are a few different models of the Slingbox available. One is just an audio/video device such as this and does not have a tuner. Another has just a tuner (no A/V inputs). The Pro version has both features plus HDTV (which I don't currently use).
Check it out at
Slingmedia's website.
Also, I have given demos of my Slingbox during our past Friday night chat session so fellow Cocooners can take it for a test drive. They just downloaded the client and attached to my box.
I also plan on visiting Slingmedia's booth at CES next week and will report on any new findings from them!