You can put road pedals on a mountain bike and mountain bike pedals on a road bike. They're just pedals -- all that needs to match are the diameter+threads on the pedal. Of course, you may not look cool using pedal X on a road bike but you will look cool using it on a mountain bike and vice versa (but this is peripheral).
The main thing with any clipless system is to practice -- its pretty unnatural feeling to be clipped into a bike when you start. You will fall and thats part of learning. (Practicing cliping and unclipping on some grass while riding or just in a doorway or trainer clipping in and out repeatedly while stationary may help) But after riding for a while, it will be like second nature. Ski bindings release either by twisting (like bicycle clipless systems do, though for reasonable sized feet you can only twist one way -- twist your heel outward rather than inward) or by some forward force (which doesn't really make sense as a regular release mechanism due to the pedaling action on a bicycle).
That being said, there are a few adjustments you can make with a system:
- Cleat position: You can move cleats back and forward a bit to make it more comfortable. You can also change the angle of the cleat to some extent depending on shoes and cleats.
- Float: You can adjust the float (which allows your foot to move a bit, measured by angle) on pedals by either using different cleats or adjusting the cleat depending on the systems.
- Tension: You can adjust the tension (how hard the pedals hold the cleat) normally by some small screw on some pedals. Setting it at its lightest setting will normally allow most people to take their foot out without much work even forcing it.
I'd start by setting the tension to as low as possible when learning and using a float setting to something not too high and not too low (the low end is normally fixed (0 deg) and high is normally 15 deg ish, but how well this feels depends on the pedal). For Look cleats, I'd suggest the grey or red (4.5 and 9 deg resp.) rather than the black (0 deg) to start with, but you'd have to try different float to see whats good for you.
There are many clipless systems on the market (Shimano SPD, SPD-SL, Crank Bros Eggbeaters, Look, Speedplay, etc.)-- some are harder than others. For example, many Shimano SPD pedals can be clipped from both sides and can have recessed cleat (so you can walk in the shoes easily), but SPD-SL can only be clipped from one side and portruding cleats (hard to walk). "Mountain biking" systems tend to be a bit easier than "road" systems (and many road bikers run the "mountain" SPD system). You may find one system works better for you than another, but you have to try them. Working with your local bike shop is best for this, because trying many at home is expensive. A bike fit may also help get you in the right position with clipless.
In the comments, Kibbee has pointed out two products which may be relevant: Shimano makes "multirelease" cleats for their SPD system, which are easier to release by rolling or twisting your foot in any direction. Shimano's Click'r system also is designed for getting in and out of easy.
Finally, clipless is not for everybody -- if you're perfectly happy with platform pedals or for some reason clipping in via toe clips, feel free to continue using it.
