(I'm skipping the startup opportunity talk.)
I'm humbly trying to develop a character page hosting service, with automated score calculation and stuff. I'm on the very start and doing it as a personal project for now. I did it with Ruby/Rails + stored on mongodb for now, as the target is to have it offered on the "cloud". And I think It could be offered as a web API
I'm on the very start for now, but does anyone think it could be worth going forward ? Or just interested on the stuff ?
More on the technical part :
Problem one, coding the rules. There's a quick path here.
Regarding the rules material, I'm using the rule files used by the open source PCGen project. PCGen is a Java software running on desktop, able to manage your character based on D20 and calculate all the scores (Attack bonus, Saving throws, weight, etc). Classes, feats, etc, are described with their impact on the character scores. So my current point is being able to parse the rule files and process them. When that's done, I can handle all rule set described in PCGen : Pathfinder, DD3, 3.5,4 and lotsa rulesets are already available.
Second part of the problem is to offer a proper web interface to that, and why not excel / pdf export/import, stuff like that. But regarding your thread subject, there would easily be a Rest web API if there's a web interface. In case it'll go public, this would be a king of open API.
Is this the kind of service you're looking for ?