Thought I'd chime in too...
I have the Slingbox Pro HD and have the SlingPlayer app on my HTC Evo. I gotta say, that this is a great invention. The SlingPlayer is great and never fails. The app for the phone is a little expensive but, again worth it. It's a one time $30 fee and there is no monthly fee with SlingBox. Only thing I wish the SlingPlayer app did was allow for HDMI out on my Evo but, that may come with an update down the road.
The SlingBox Pro allows 3 inputs. I have DirecTV, Roku (for Netflix) and OTA hooked up. Keep in mind though, the SlingBox is like a TV meaning if you are watching a show via DirecTV using your SlingBox, whatever TV you have hooked up to that same DirecTV receiver will also have to watch the same show. That is why it's nice to have multiple inputs so that you don't interfere with those at home.
With a SlingBox you'll always have your favorite TV wherever you are as long as you have internet. Very nice in combination with DVR. There are a lot of older SlingBoxes out there so, to be as "future proof" as possible, I'd suggest the SlingBox Solo or SlingBox Pro HD.