After you download TMPC, you log in with your twitter account (or create a new one, if you don't want to junk up your old one with commands), and then you're set. You can also set your Gmail account for certain commands, some of them are listed below. There are built-in commands for TMPC, most of which are incredibly useful. I'm not going to copy+paste them all over here, so if you want to know all of the commands, check out the Codegeeks website.
-shutdown/standby/lock - Shutdown, standby, or lockyour computer from anywhere. Useful if you remember that you left it on.As you can see, TMPC has some crazy commands, getting right down to process management, all without ever seeing your computer screen. After you Tweet one of the commands, TMPC will respond on Twitter with whatever action was run, like "TMPC -> Setting Workstation to Standby Mode". Even with just the built in commands, TMPC is an amazing program. But you can also have custom commands, making TMPC launch any program you want when it senses a certain one-word command.
-screenshot - Tweet this, and TMPC will screenshot your PC and upload it to TwitPic.
-getprocesslist - This will make TMPC e-mail (via Gmail) a list of all running processes on your PC.
-download - Download anything. Just specify a URL after the word 'download', and TMPC will download the file to whatever directory you have set.
-getfile/getfilelist - Probably the most intriguing; "getfile" will automatically upload the file you specified as an attachment and e-mail it to yourself. If you don't know the full path, using "getfilelist" will help you get there.
As for the physical aspects of the program, TweetMyPC is only around 1mb in size, and runs fairly hefty at 17MB in RAM. It is not portable, however, because it requires Microsoft's .NET framework 3.5 to run. It is open source, however, so any who want to look at how it works can.
It's a strange program in the sense that everything that is done is available online for everyone to see, but it is ingenius nonetheless.
Visit TweetMyPC (CodePlex) website for download