Here is one way you could solve the upload issue for mobile browsers:
The mobile web version of Facebook and TwitPic use this design pattern too.
As far as I know, there is not yet an HTML5 way of doing this.
The solution is to wrap your project in a native app using Apache Cordova (formerly known as PhoneGap). This wrapper exposes native functionality as a Javascript API. A custom widget can then upload photos from the camera or camera roll.
A tutorial about using Cordova is being written and will appear soon!
Update: here is the link to the tutorial already!
I thought it would be possible but in short it is currently not possible for the iphone.
Stack overflow pointed out the following though, IOS 6 is said to support photo upload to websites. Then again since the beta has only been released like yesterday this might take a while.
If you still would like to have an android version of the file upload see the following video: http://www.youtube.com/watch?v=4f2Zky_YyyQ
Also you should have a look at this site on a android mobile device.
According to the video the following tags are allowed:
<input type="file"accept="image/*;capture=camera">
<input type="file"accept="audio/*;capture=microphone">
<input type="file"accept="video/*;capture=camcorder">
<input x-webkit-speech>