I've gotten pretty far along with an online IDE, but it isn't quite ready to be released yet. I really need to find a way to load the firmware to an arduino from a phone/tablet. Most phones will require some sort of adapter and can load the firmware via the headphone jack.
Tablets that have USB ports just need an app that can see the USB serial port and load the firmware, all compilation will be done remotely.
If anyone is interested in helping with creating an app for USB enabled tablets, please let me know.