If the inventor will please make a portable, electric burr grinder I would be extremely happy. This is the missing piece, for travelers and those who cannot otherwise own a proper burr grinder.
I've been using the Hario hand grinder and I find it extremely difficult to maintain a grip. Is the Portlex easier to hold? I'm female thus possible not as strong as others who may be using this.
I have owned both Hario's generic handgrinders and I swear by Porlex. It's higher quality construction and easier to hold and use. It also snaps right into Aeropress for travel so they are a perfect combination. If you get one, get the mini as there's really no reason to buy the large one.
Which of the two Hario grinders are you using? I have the mini mill, and use it daily for my aeropress without any annoyance. But you need to have a quite coarse grind (no finer than filter grind) and do an inverted brew. Grinding out something like espresso fine coffee is a pain.
Edit: came across this which looks promising http://handground.com/