This project is a proof-of-concept created at the 2016 White October Hack Day.
It provides you with a one-page overview showing you the oldest unread message in each of your channels and DMs.
As this is only a proof-of-concept, there are lots of areas that need improving.
The most important is to do authentication properly using OAuth, rather than providing the token directly, which is very insecure.
Following on from that, it might be nice to improve the look and feel, and probably use a templating engine rather than writing the HTML directly.
It looks like Slack have implemented something similar themselves: https://slackhq.com/a-new-way-to-catch-up-in-slack-148857029091.