I already got this queued as a RPG PlayMaker Kit. Which will come with the inventory system.
However it's halted right now, as I don't want to proceed with the current Unity GUI. It's too heavy for mobiles. Also, I'm reluctant to make it dependent on NGUI. I'm waiting for Unity 4.3 to come up with some native sprite based GUI support. I hope to finish that kit with that.
In the meanwhile please let me know what's troubling you in creating the inventory system.