I recently developed a native iPhone app for remote managing your Transmission transfers on your iPhone / iPod Touch. You can use it to start/stop/view your current downloads, but it also has a built-in browser you can use to download torrent files and send them to your Tranmission client. This makes it possible to start new transfers from your iPhone / iPod Touch, wherever you are!
iGear is currently pending for review, and will be available in the AppStore as soon as Apple approves it. I hope you like it.
Here's a screenshot:

For more information visit the iGear support page: http://p-development.nl/software/igear.
Offcourse any feedback and feature requests are more then welcome.