It looks like EyeTV is doing what Sling and HAVA can't.  They are allowing iPhone users to watch their TV broadcasts over 3G.  Electric Pig is reporting an easter egg "workaround" which allows streaming over 3G.  They explain:

Elgato’s EyeTV app requires you register your Mac to its free My EyeTV service in order to tap into broadcasts outside the house, but use it when your iPhone has only a 3G connection and you’ll see an error pop up, warning that “Live TV playback requires a Wi-Fi network connection.” Tap the OK button, and the app will act as if it can’t receive broadcasts. However, tap the text of the warning message instead, and the Eye TV app will stream live TV over a 3G connection.

Apple is likely to put the kibosh on this one pretty quick so if you have an EyeTV and want to do some TV streaming, you might want to download the App ASAP and hold off on updating.