rsilk's comments

Great list. I really appreciate the graphic used to distinguish platform support (responsive vs not). Much easier on the eyes than a written list of supported screen sizes for each framework.

Would it also be useful to list the underlying language used for each framework (plain CSS, LESS, Stylus, etc) in case you plan on customizing?

I think this is an interesting idea. Easy to bolt on to existing email providers, and client-side support for this feature could be implemented incrementally.

I wonder what kind of privacy implications this could have (and whether or not we care)? For example, someone could set up a tool to repeatedly poll your service with different parameters over time to get a sense of your daily habits/schedule. (I suppose if this was a concern then you probably wouldn't use this service in the first place.)

Overall though I think this could at least provide a better alternative to clunky out-of-office autoreplies. The sender could make better decisions about where to send an email if they knew ahead of time that their recipient was going to be unavailable.