An interesting thing about smartphones is it's capabilities as a remote access device. Quite literally, you can control your favourite BitTorrent client directly from your Android device. All that's needed is a little setting up on your torrent client, router, and the Android app called Transdroid.
Now why would you want to remote control your torrent software from your smartphone when you could just sit in front of your PC and do it in much more comfortable fashion? I could think of a few reasons:
You're not the only PC user. You don't always have access to it but you've set your favourite client to always run in the background.
It's not your PC. You have a PC at home, but it's your parent's or maybe older sibling's. You're just borrowing time.
You're not always at home. Whether it's for work or leisure, you tend to not be around at home. You've probably set things up as a server that's running 24/7.
You're a geek. You do it because you can. Or, maybe you just feel curious like me.
I'm sure the brilliant minds on the Internet could come up with many more reasons than me. Now that you've motivated yourself to give this a try, all you need to do is download and install Transdroid on your Android device. It's currently not in Market, so you'll have to manually install it.
Next up is, of course, setting things up. I'm currently testing with a Transmission client on Ubuntu while Transdroid is on my HTC Desire HD and it's working perfectly. Other clients are also supported, and on Windows/Mac/Linux. There's something for everyone. The instructions are simple to follow.
If you happen to need help setting up port forwarding like I did, there's help readily available.