I only recently found out about Prone
It turns exceptions in a Ring app into nice interactive stack traces where you can inspect the request and stuff like that. The README links to a great demo video.
I'm keen to add it to Chestnut, it seems like one of these obvious developer happiness things, and that's what Chestnut is all about. With the current setup it's also quite easy to have it in dev mode, but leave it out in production (not a good idea to have stuff like this in production, it's bad for security.)