Pneumatic air control systems have been around in model railroading for over 50 years. Three former manufacturers---Del-Aire, EZ-Aire, and Sunset Valley --- are all now out of production, but I still have many pneumatic air components available.

Air motors (also called pneumatic motors) are about the same price as electromagnetic switch machines, but offer far superior performance (not to mention that they don't dim the lights on the rest of your layout while being energized).

Here's why they perform better. Air-motors are continuously applying a force to the points — either by the air pressure pushing one way, or by a spring pulling the opposite way. Therefore, the points are held against the rails at all times regardless which way the switch is thrown. Using air motors, you will never have a derailment caused by wheels having to "pick" which side of the points they will go.

Another advantage is that pneumatic motors typically use a toggle switch, not a push button, so the direction of the toggle can also serve as an indicator of the position the turnout is in. 

Using air-operated switch machines requires an air source, but you don't have to buy an expensive air compressor. All you need is a portable air tank of some sort. This could be something as robust as a compressed air tank sold at Wal-mart, etc., or as simple as an empty 2-liter soda container. An inner tube even works just fine as an air reservoir and will last for weeks between refills. When you need to refill your air "tank," just take it to the neighborhood gas station and pump it back up again.  A pressure of about 40 psi is all you need.

Not convinced yet? There are still several additional advantages of air-operated switch machines over electromagnetic ones that I haven't covered yet.

• First, there are no coils to burnout. You can expect air motors to last your lifetime... and then some! 
  
  
• Second, with traditional switch machines, it's a time consuming art to get adjustments just right so that the points are against the rails either way the switch is thrown. That's because the range of the throw in a traditional switch machine throw was just about the same distance as the movement of the points. Once you have it right on one side, throwing the switch the other direction would not put the points against the rails. With air-operated motors, the throw range is about 2 to 3 times the range that the points move. Most of the time after installing the air-motor, you don't have to make any adjustments at all. 
  
  
• Third, ease of installation. With air motors, only 1/16" plastic tubing is used to route power. As a result, you have no maze of electrical wire running under your train table. Using a manifold, you can even control multiple turnouts from a single toggle ! Manifolds are available with 4, 6, 8, or 12 outlets.
  
  
• Fourth, air motors can be used for much more than switch machines. For example, you can use an air motor to pull down a gate to allow pipes to roll onto your flatbed. The possibilities are endless.   
  We use it on our club layout to operate a rotary coal dump !