I've never seen this anywhere else, but it seems like a good way to prevent the frustrating occurrence of accidental clicks while scrolling. What do you think?
The two principle mouse/touch events in question, which the OS fires (to the application) are:
There is actually a rather complex mechanism behind how the OS determines whether a gesture is the former or the latter. I'll be demonstrating it with mouse (for common terminology sake), but it works the same for touch. It goes:
A properly implement application should respond to a click event and not mouse-down or mouse-up events (which may cause the issue you are describing).
So it's really that you either get a click event, or if the user moves the mouse/finger it will be a drag event (so long the move is bigger than the given safety area). Thus even if the UI doesn't support scroll (and it is possible for a list to appear as if scrollable while it isn't) once the user moves the mouse/finger there wouldn't be a click event.
If my memory doesn't fail me, the actual OS safety area is not in pixels, but in inches instead (so higher resolution screen won't have a smaller safe area), and it may vary depending on the OS tracking speed.
To conclude a properly implemented application should not suffer from the issue mentioned. Regardless, the safe scroll area seems to me:
I would say yes to it being a good idea. No doubt there are plenty of people who experience the same problem you have. They will welcome your solution. And I don't see how people who don't have this problem will we opposed to this idea as long it doesn't take up to much space.
I would say no to it being good ux. That's because I'm considering the way people will hold their device, the reach of their thumb or finger is limited in some ways, and the fact your limiting the interaction possibilities.
According to this image, right-handed people will be forced to hold their thumb in an awkward position in order to scroll on your safe scrolling area. Left-handed people will have less problems.
In this position the thumb or finger has more reach and people will have no problem reaching the safe scrolling area.
In this position the reach of the thumb is limited in the portrait position. Only small dragging gestures are possible.
When I scroll, usually with my thumb, I don't move in a straight line up. My drag will have a curve to it. I know the scrolling will not be limited to the safe scrolling area, but adding that bar will suggest it is. Therefor you'll be forcing people to perform a certain movement within a limited area.
But it might work out. It would be awesome if you try and succeed, introducing a new and safer way of scrolling. So you could try it out and see what real time users think of it.
The general rule in mobile is just to detect drag vs. tap. Instead of adding a specific gutter for scrolling, could you try detecting when the user's gesture is a tap or drag?
You don't have a lot of real estate on the screen to start with, and you can't ever guess accurately what's going to be enough pixels (in width) for one user's finger vs another.
Perhaps it'd be better to use submenus (group your items) instead of having a menu that a user needs to scroll. It's a click or two more but it cuts out the need to cripple the UI unnecessarily.