Shimano have had an integrated brake/trigger shifter since the introduction of the Nexus 8. They were on a Ridgeback I test rode in 2004. The action would have been harder with winter gloves on than twist grips, I wouldn't know about without, I always ride with at least mitts. The only new stand alone trigger shifter I've seen is part of the Alfine range, though the action looks the same as the integrated one.
You have to remember how different the Rohloff shifter is to everything else, the need to pull in each direction rather than depend on a sprung action is what makes the shifting so reliable. It probably also makes designing alternatives harder.
