Your iPhone plays audio. Your iPhone plays video. Until now, you had to sync those suckers. Today, the insanely brilliant iPhone Hacker core announced a preliminary version of a Transmission Peer-to-Peer client for iPhone. The code is ported from the Transmission site to run on the iPhone's ARM microprocessor. Tests on downloaded files produced the identical MD5 checksum as downloading via wget.
Now before you start torrenting, there are some important matters you need to know. First: P2P + EDGE do not mix. Let me repeat that for emphasis. They DO. NOT. MIX. That's because EDGE + P2P takes down EDGE faster than toppling a Jenga pile. Update Further testing has gotten 5kb/s over EDGE without crashing but it's an iffy proposition. Use with care.
Second, we are posting this because there are many *legal* torrents, including music and video, available for download. So please don't start getting into a "Torrent Good"/"Torrent Bad" flamewar in the comments.
Third, this is EXTREMELY preliminary software. It will develop over time -- so you probably don't want to grab a copy and start torrenting right away until it becomes more stable.
Fourth, this is a command-line client. As it matures, someone is going to slap a GUI on that baby but at this time, do not look for the software to show up in Installer.app or Cydia.
Finally, be aware that torrenting will wear down your battery faster than, um... toppling a Jenga pile. (C'mon folks. We're really short on family-friendly metaphors here. Suggest your own in the comments.)
Way to go core!