This is great, but it would have to be done with something on your own PC. I've been wanting to build something for this myself.

The issue is, posting requires your posting key. For security reasons, Steemit doesn't actually store your keys. Your "password" is similar to the 12 word seed in bitcoin wallets, it's used to generate the keys of your account.

This could be done however, with an application that ran in the background on your PC, assuming you keep your PC on most of the time.