A great looking (brandable) typing speed test like http://keybr.com/ maybe? Would be a great plugin that would sell I'm sure and I need it!
I can do this.. but I need more details...
Do you want to store the results?, would you like to create your custom texts? What do you like?
I still think it's a sellable idea but I won't be using it for the reasons I posted a few months ago at this point. Lemme know if you do build it :)!
send ma (PM) with the full specifics. Ill give you an honest hand.