Taking a closer look at Authority Labs at the moment, and another tool/service called getstat which looks good - though at a price.

Any other similar services out there?  Full hosted, automated rank checking?

Only ones I have found so far are:
authoritylabs
raventools api (uses same data - but more convenient if you are looking for other stuff as well)
sistrix
and google docs import xml

I haven't actively been looking for SERPs data mind you - those are just ones that I have noted whilst looking for some related stuff.

Thanks for all the comments in my (very) extended absence! I am still planning on building my own partly because I really need to get back up to speed on the coding front and it's a project I am interested in, despite the delay in getting started but also because I've still not yet found anything that exactly meets my needs. The main question remains which language I go with.

That said, after a few mentions of Authority Labs, I am checking them out at the moment. They offer a 30 day free trial on their pro version (50 domains, 1000) keywords although I would probably look to use the api if I was going to go with them.