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I have a setup in mind, which involves a magnet put next to a reed switch, times 2. So it should work so that a reed switch is only activated when two magnets are stuck together and next to a reed switch, and deactivate once there's only one magnet next to it.

So I have found a couple of products from this at Sparkfun:

http://www.sparkfun.com/commerce/product_info.php?products_id=8642

I am in need of magnets where the strength of the magnet can be varied. Specifically I need 3 "settings", off, low and high. Low would be where the magnets have enough strength to connect but not more strength than they can be pulled apart. High would be where they connect but can't be pulled apart.

I've been reading up on robots, and in one of my books there's a chapter called Multiple Robot Interaction, which mentions having one robot as the queen, and the rest as drones. There are several ways of connecting, WLAN, Bluetooth, Infrared and I'm sure I'm forgetting lots of others. But which is the most commonly used/best way of connecting?