It would be really handy if there was the ability to send something to an email endpoint and have have a smartapp respond to it. There are a bunch of devices that don’t offer a webhooks but can send email alerts when something happens (Insteon i’m looking at you).
Currently i’m looking at a site called pushingbox that allows you to send an email to either firstname.lastname@example.org or to email@example.com with the subject: and it can then perform a post or get to an address. They also let you add json variables in the body that can then be used in the http calls.
If we had something like this for smartapps we could get instant alerts without having to poll continually. Not sure if it’s viable but just thought i’d suggest it.