I love the USB Host Shield. I have been using it at work all day every day to let my foot pedals act as modifier keys (shift, alt, cmd) for my keyboad on my Mac.
Beware though, there are some boards it does not work with. e.g. the software does not yet support the Arduino Zero (apparently it is on the roadmap).
https://github.com/felis/USB_Host_Shield_2.0/pull/202#is-
suecomment-216075846
Rating:
[5 of 5 Stars!]