I've a smart list called @Calls, where all my pending calls go. And I like to put the phone number next to the caption, so I don't have to bother looking up the number to place the call. But, you know, the iPhone app does not support the usual phone links, where numbers are recognized and made into links, that upon tapping initiate a call.

I just discovered that I can place the number prefixed with "tel://" into the task's url field (eg. tel://12345678), so, I just need to tap this url in the iphone app and it starts to dial. YAY!
I didn't know that, and a quick search of the forums here didn't bring it up either, so, hope some of you find this useful, too!