Personally I don't see a problem with you or anyone else taking on these types of arrangements providing it is clearly disclosed in advance that rewards either financial or otherwise were received in relation to the promotion of said products or equipment, at the end of the day you have a business to run, family to feed and an internet connection that costs money for the main benefit of others.
This particular one shown mentions nothing about giving it a favourable review or that a project which may incorporate the device in question has to work in any particular manner or at all, their statement of "we would be happy to provide you with any key massaging that you can incorporate into your video" could be interpreted as a paid script by some but I doubt very much if anybody with any dignity would follow their script to the letter, certainly not the Dave I know anyway, tell them you had to improvise and didn't have an any key handy.