Have been reading about a possible solution to get SLINGBOX and XBMC to work together as server, and client. It is an expensive solution but might work well for some in certain situations.
The cheapest solution is still to get you SLINGBOX on your remote vacation cabin television is just to use your existing ITOUCH, IPHONE, IPAD running the $30 client, and buy the $30 - $40 audio-video cable for the ITOUCH-IPAD-IPHONE. So $70 and you have SLINGBOX PLAYER playing on your TV to echo your home TV which has the attached SLINGBOX.
Or, you can use the JACKSTA RECORDER software on your home workstation, to TIVO (record via DVR like action) your existing SLINGBOX in your local network. Costs $40. This will save the recordings as ITUNES compatable videos, and link them into ITUNES. Then you can use the XBMC to remotely play back that workstatation video files (or whatever tool you use for access from ATV2 to a remote server).
Have fun tinkering.