I've had the need to write both of these in a script currently under development. RSBuddy's price API didn't seem to update often enough (or just not return the proper data).
The PriceLookup API uses Jagex's JSON API for their website.
The Item ID to/from Name API uses a (relatively modern) list of IDs and Names which I added to database. Simply change the function being executed in the URL and enter the proper argument.
Downloads can be found on my website b