Hi HN -<p>My partner and I just launched Zenlogin. It's a super-straightforward security API that you can integrate into your login flow, whereby if/when we detect a suspicious login (via things like IP and User Agent), we'll send off an email to notify that user of the login action.<p>While we were building out this security functionality for another app, we realized it's pretty tricky to get right. We had consider VPNs, Bots, dynamic IP addresses, etc.<p>A simple use-case is: a user logs into your app from Toronto, and then a few hours later logs in via Atlanta. In that case, we'll send off a (v nice looking) email that includes a Google Map and details on the login. Something like:<p><a href="https://zenlogin.co/preview" rel="nofollow">https://zenlogin.co/preview</a><p>Happy to answer any questions :)