Last Night’s Checkins gives a heat map of all the places you’ve ever checked in.

The part of Foursquare that I’ve become most enamored with lately is this ability to create a lifestream of places. Can you imagine if you had all of this data from your teen or college years? This would be amazing to mashup over long periods of time.

I’m going to build a stupid simple Foursquare app that emails you the places you checked in one or two years ago on this day.