iron.io would be an excellent resource for you. It offers an amazing task scheduler. You could easily write a quick website scraper and set up an iron.io worker to run it at whatever your desired interval is. I've used it before alongside Twilio to create a simple app to text hourly reminders, and found it painfully easy to do, especially in Ruby.
Also, I assure you that pulling market information is perfectly fine, as it is not stated otherwise in the rules or ToS, and Tektek themselves pull various data off of Gaia as well.
Something you may consider doing is making a Chrome and/or Firefox extension to add functionality to Tektek's item database. That way you only need to write that one feature, and you won't have to design your own website (because we all know that real programmers can't do UI/UX, better yet art). Also, if it gains enough popularity, whoever runs Tektek may contact you and work with you to integrate your code.