One of the good things about the "very sweet solution" of iPhone development is that you don't need any special tools or too much knowhow to create neat applications-- if you know a little HTML, a little PHP, and have access to a text editor, you can come up with some pretty cool stuff. This tutorial from IBM's DeveloperWorks is about as simple as it gets, and yet it shows you how you can use your iPhone as a remote for iTunes, Keynote, or any other AppleScript-able applications on your Mac, with no jailbreakin' necessary.
Of course, as he mentions at the end, Telekinesis did most of this stuff early on, so if you've got something standard that you want to do (like control iTunes), you don't need to write the code yourself any more. But combine the tutorial with any other custom AppleScripts you've written (or might write), and a lot of possibilities open up in terms of what you can do with your computer, straight from your iPhone.
[ via MacBytes ]