The is called Smozzy, and it is free in the Android Market. It's really awrapper for the built-in browser, but whenever you click a link, instead of sending packets to the remote web server, a request is sent to Smozzy’s own server via SMS. Most URLs will fit into the 160 character limit of SMS, but even if an URL does not, Smozzy will simply break it up into multiple text messages.
The Smozzy server downloads the web page you’re trying to visit, and then encodes it as a ZIP file. The file is transmitted as an MMS file, and once the ZIP reaches your handset it is decoded by the Smozzy client.
It's not going to reach 4G speeds, obviously, and not even 3G. It also requires an unlimited messaging plan as you're going to using a ton of messages with the app. Finally, Smozzy does not currently support SSL, so just remember that and don't do anything silly like online banking using this method.
Additionally, this only works for T-Mobile, and you can bet once T-Mobile figures it out, they will shut it down. In other words, it's a nice little proof-of-concept, but it's probably not going to hang around for long.