Lots of different options, and a quick search for "kite aerial photography" will give you a good overview. I am using a flowform kite (because it packs up very small; approx. 100 € for a 2.00 x 1.45 m kite which is strong enough to lift a point-and-shoot camera under relatively light wind) and have used a Canon A3000IS (because I got it very cheap - only 30 € for a used one) but will probably use a different Canon powershot camera in the future. Perhaps the trickiest part is the camera rig. I have the impression that most people use the Picavet rig (explained for example here:
http://www.arch.ced.berkeley.edu/kap/equip/picavet.html) which is somewhat complicated at first glance. As the worst thing that can happen (in terms of image blurring) is rotation about the optical axis of the camera (and the second worst any rotation about any axis close to the camera), the purpose of the rig is to keep the camera pointing in a certain direction without rotating. I have used a modified version of Scott Armitage's S4 rig (
http://www.personal.psu.edu/nmc15/blogs/anthspace/2010/05/two-light-and-low-cost-kap-suspension-systems.html) and quite liked it for its simplicity. With KAP in general, gusty winds will make it difficult to take good photographs, but under stable wind conditions this works ok. Last but not least, yes, CHDK will give you almost unlimited opportuinities to control most Canon powershot camera using scripts. From my perspective, this is the way to go.