[HALtheWise]

At least on my Android Google keyboard, that exact feature exists (swiping left from the backspace key deletes words in a natural way). Similarly, swiping on the spacebar moves the cursor. More generally, swipe typing, aggressive autocorrect, and voice input are pretty novel and core to any modern phone keyboard. If you want to see really wild stuff, look at some of the Japanese phone keyboards, they're mostly based on slide gestures that can translate to a physical keyboard.