At our internal Hack Day last week Yahoo! engineer Pradeepta Dash showed some neat tricks with his iPhone app called iFlickr. While I can't share the details of his hack, Pradeepta did give me permission to share some of the stats on iFlickr from his AppID usage report to date.
iFlickr is a capture and auto-upload application for your iPhone camera. Once you authorize the app on your iPhone, you can start taking pictures and sending them directly to your Flickr account. You have privacy and tagging options, but, best of all, Pradeepta uses Yahoo! ZoneTags to capture location data which gets sent along with your photo. I'm also enamored with the resolution of the images iFlickr gets from the iPhone camera.
Now, it doesn't surprise me that he has so many users (well over 5k as of this post), but I am actually a little surprised at how active those users are. You can see from his AppID report that iFlickr is uploading over 300 images per hour. Impressive.