The slingbox app for the iPhone is a little expensive but it works well. I use a slightly older HD Slingbox. The newer ones with HDMI I hear don't work well due to DMA, and they don't work on a Tivo. You'll want to use component cables What your setup will most likely look like:
1. You connect you slingbox to your router. It says in the manual not to use wireless. I use a wirless N gameing adapter and it works fine. You will want to follow the setup for port forwarding for the slingbox. You'll find it in the setup process under "Setup Internet Viewing"
2. You wire the output from your cable box to the slingbox, then wire the slingbox to the TV/Receiver.
3. Theres an IR device that you place in front of your cable box and attach to the slingbox. This is how the slingbox will control the cable box.
Keep in mind this is a single user system. So if someone is home watching the cable box, and you fire up the slingplayer, you'll be changing channels on them.
Also if you want to hook a TV to the deviced on the receiving end, you don't have to use an iPhone. You can use a Mac or PC laptop to receive from your slingbox, and the app is free for computers.