No word yet when this app will automatically cause the iPhone to ring as you approach an open manhole cover. While we wait for that functionality to be added, let's move on to three iPhone apps I actually find useful, especially for mobile professionals and other frequent travelers.

I've before. Reason: It's one of the most useful productivity tools for those times when you're on the go. And the iPhone app is a nice complement to the service.

In a nutshell, the (US$4 to $13 monthly; $7 for 5 minutes in a pay-as-you-go plan) allows you to create a quick voice memo to yourself, or to someone in your contacts, over the phone. The message is quickly, and most often accurately, transcribed and sent to you (or others) as an e-mail or text message. Jott lets you maintain to-do lists, add appointments to your Microsoft Outlook or Google calendar, create a Twitter tweet, and a lot more--all by phone.

The free puts an easy-to-use interface on the Jott Assistant service. You can start a new voice recording with just a couple of taps on the screen, for instance, which is ideal if you're moving around. I subscribe to the $4 monthly Jott Assistant plan, and I highly recommend it, though I wish you could leave messages longer than 15 seconds. (For that, you have to upgrade to the $13 monthly plan, which feels a bit too pricey for me.)