Let the user set a trigger to open the trunk and/or frunk the next time the key (phone or fob) is detected. Useful when you expect to return to the car later on loaded with shopping bags or a walker.
Although not as flexible as using the camera to detect gestures (another suggested feature), a click on a button on the screen as you exit (or perhaps triple-click on the fob trunk button) could set it to auto-open next time your key or fob is detected. When you return with your hands full, the trunk will open when the fob or phone key is detected within range of the car.
(lightly edited by moderator)