Is there an API? I mean, Trade Hangout got a gui above head :P
And yes, I know i don't have a scripting example, because i simply don't know how.
There is no official API to get the RAP of a player if I'm correct.
You'll need a web server to build something that fetches the RAP of a player. But the thing is that decent web servers cost real life money. There are some probably some servers around that act as a proxy to www.roblox.com's API. So using that you can probably fetch the complete inventory of a player and combine the RAPs. But this will as stater earlier real life money, but you'll need some experience with another scripting or programming language. PHP is probably the best for now.
But if others do it, it means you can most likely take a share of their web servers too. :3