On a whim I bought a Lidl copy ages ago. It was cheap, although not rock bottom, and it works well enough. It has no built in screen (told you it was ages ago) and the wifi only works with older versions of Android. But as I am not big on sporting activities it suffices on the rare occasions I get it out of the cupboard.
I did get a cheap knock off one to take on holiday last year. The still image quality was appalling, the video not much better, and I sold it to cash converters as soon as I got back. The Lidl one works so much better.