I'd say it's an idea at this point that won't give you the install and forget soution you are probably looking for. The issue isn't on the sending side ( slingbox ); it's on the receiving end with having limited options on what to connect the TV to in order to receive the slingbox stream. A lot of people in the past were using the discontinued slingcatcher in place of their laptop as a way to receive their slingbox stream on another TV in the house, but that required an ethernet cable to be plugged into it to receive the TV signal due to it lacking in being wi-fi enabled. It wasn't the most elegant solution, because if you could run an ethernet cable, you could probably just run a coax cable which would defeat the purpose of having a slingbox. That leaves going in the wi-fi connected device direction with either the googleTV option or the Boxee option. I use a GoogleTV enabled logitech Revue and at this point, there is a major bug that freezes the screen when you change channels or access any functions on your cable box rendering it frustrating to use. Also, the picture is reduced to a lesser quality level than it is on the slingcatcher, so I can't wholeheartedly recommend you go in the GoogleTV wi-fi direction until sling gets the issue fixed which will require a Google O.S upgrade. I haven't used the boxee box, but I know they are dealing with a few issues as well.
Bottom line; since the GoogleTV and Boxee hardware uses wi-fi to receive the stream from the slingbox, it would be an ideal solution for you to send the signal from one part of the room to another, but you'd have to accept the teething bugs that, at this point, haven't been fixed in both platforms.