Proof of concept web extension for Firefox, which queries data from Steam's dynamicstore/userdata and imports games into IsThereAnyDeal's Waitlist and Collection.

Feel free to fork this and update in any way you feel like. If you want to test it out, you'll need to get your API key and OAuth Client ID here: https://isthereanydeal.com/dev/app/

To install web extension in Firefox, access about:debugging