Keyboard that can hold keys down for hotkeys

Hey all,
I tried the typewriter and it only works for typing one letter at a time, but I was wondering if it would be possible to make a keyboard controller layout that allows keys to be held down for hotkeys in photoshop, after effects, bender, etc.

In addition, it would be amazing if instead of holding a key down it register a single tap as a hold [down] and a second tap on that key as a let go [up].

Thanks!