This service streams video and audio. For iPhone it is only available if you "jailbreak" (hack) your phone.
I have found it works rather well IF you have the bandwidth. So for example if you are on wifi with a good link. Or if you are on 3G with a good connection. Over normal cellphone data (edge) it is too slow to work.
It's a cool service, you may also want to check out the competing service that supports iphone,nokia : flixwagon