Lego Deal Finder
It's a Python script that I wrote that hunts for underpriced sealed LEGO sets on eBay and pings you when it finds one. Each run it pulls the 200 newest sealed Buy-It-Now listings from eBay's "Complete Sets & Packs" category via the Browse API, then figures out the landed price — item plus shipping to your ZIP — rather than the sticker price.
For each listing it regexes the set number out of the title and looks up the set's market value on BrickEconomy. A deal gets flagged when the landed price is at least 25% under market value and sends a message to me via Imessage. It runs every hour to make sure I never miss a deal.