Here's an Startup/SaaS idea you might like to try executing on:
Finding out your public IP is a funny fundamental problem on the internet -- turns out one of the easiest practical ways is to actually just ask some other device outside the network!
Turns out it's actually quite taxing to run this service (despite it's relative simplicity), and so many people used it that it made HackerNews when they shut it down. The site was getting 30B requests a day -- I'll let you do the math on if what this could be worth if you can get 1% of people who need/use this functionality to become paying customers, and get them to pay some reasonable amount per 1000 requests.
There's some risk here of technical difficulty scaling up (30B is a lot of requests), but if you start small and make sure to build in profitability from the get go, sell to proper enterprise clients who may need SLAs, security features, or latency guarantees, there's lots of meat on this bone.
NOTE This might also be a fun project for trying out something like Cloudflare Workers or other gratuitous free tier functions-as-a-service providers.
This was originally posted @ Unvalidated Ideas (Edition 4)