It can be done
To mimic iphone and touchflo in B4PPC just read mouse movements and translate them into gestures. This works for one-finger gestures but I hear the iphone just "pinch" gestures also, that is, it can react to the way 2 fingers on the screen move in relation to eachother.
Pinch is not possible yet on Windows PPCs.
I have tinkered around with gestures a couple times and if you keep it simple it works great. For example, if you break the screen up into a grid and designate each cell of the grid a letter then gestures just become a short string of letters.
Screen grid:
.A.|.B.|.C.
.D.|.E.|.F.
.G.|.H.|.I.
.J.|.K.|.L.
Gestures:
Horizontal swipe right: DEF or GHI or ...
Vertical swipe up: KHEB or ...
Clockwise from left to top: GDAB or ...
and so on...
From there it's just a matter of reacting to the gesture. Animate an image, slide a panel in from the side to simulate page turning, etc. Using a couple of the image libraries found here I was able to create an app that browses images thumbnails, zooms, and rotates images purely using gestures in the above manner.