Does anybody know what the open ended foot straps used on kite surfboards are called and where you can get them?

North used Skyhooks on some of their boards, circa 08/09 but you probably mean predator footstraps.
try here
http://www.towsurf.com.au/towsurf.com.au%20-%20accessories.htm

Northshore industries - they used to have them on their site.

I made some out of Aluminium and foam which i use for my back foot on my wave board. Gives me great support for my foot and easy to get into and out of without having to move my foot off the centreline. Also lets you put your back foot where you want. I love mine, but lots of people don't.

predator footstraps, the inventor lives south of sydney, Sean is his name, PM me and i can give you the phone number, he is a kite surfer.