MobiTV is a monthly paid service. I believe it's $10/month and channels vary depending on service provider. Google MobiTV and find the link to their website for more info.
If you're looking for something "free" monthly, i suggest using a slingbox. There is a 1 time investment, but you can watch anything you want, instead of the 15 (or less) channels you'd get with MobiTV. It's nice to pick what you wanna watch and not have to watch whatever those channels put on.
It's worth the investment. Trust me.