Something missing from many location-aware Twitter applications for iPhone is the option to stick a Web map into a tweet. Most simply change the home city in your Twitter profile and slap on some latitude and longitude coordinates. This is great if you feel like looking those up, but otherwise it's a less than ideal way to tell people where you are.
Schmap, the social-mapping service, has a new and free iPhone app out called GeoTweeter (not to be confused with GeoTweeter.com) that lets you do just that. You can broadcast your location on a map that gets sent at the end of your tweet. Each map link takes up just 23 of Twitter's precious 140 characters, leaving you with 117 to tell people what you're up to.
To compensate for this lost space, the app lets you add a rating, a photo taken from your phone, and any "notes" you want to jot down about the location. None of these will show up in your Twitter message, and instead are put on the maps page hosted by Schmap. You can access these pages both on your phone, and online. If you've used Place Saver, Schmap's other iPhone application, the functionality is almost identical.
One feature that makes it quite similar to geo-social network Brightkite is that you can use these geo-bookmarks again and again once they've been saved. You get the option to re-tweet it at any time, which will append the location link to the Tweet, letting people know where you are, or what location you're talking about.
Something this application is missing, and in dire need of, is a way to view messages from your Twitter contacts. It's very good at letting you post to Twitter, but the fact that I have to go and fire up another Twitter application, or my browser to view messages is a big oversight. Once that's in there, I could easily see this becoming one of my favorite iPhone Twitter apps.