There's so many good third-party applications out for the iPhone right now, not getting your iPhone jailbroken sounds a tad criminal. Here's one of the better programs for Apple's mobile by homebrew developer sunburst: Torrentula, a BitTorrent client for both the iPhone and the iPod Touch.

Do take note that Torrentula requires the newest Jiggy Runtime. If you haven't downloaded and installed Jiggy yet, then you need to do so and you can check out how here. Once you have it installed, just add the source http://itouch.rockt.es/repo.xml to your iPhone Installer.

Once installed, just follow these steps outlined below, courtesy of sunburst:

Download .torrent files to your device with the HistoryDL.app (recommended) or the Safari Download Plugin into the mobile (or root)/Downloads folder. The program will scan your mobile (or root)/Downloads folder for new torrent files, and will import any valid torrent files regardless of their filename or extension. When a torrent has finished downloading from peers it will be automatically moved to mobile (or root)/Media/Downloads when selected. Note: Torrents continue downloading even when program is closed. A device restart can often activate/fix stubborn torrents.

Got it so far? If you still have any questions, you can just choose to drop by Torrentula's thread, linked below, for more information.