With reference to
http://www.zionworx.org.uk/forum_3/viewtopic.php?f=20&t=858&p=3829&hilit=Si600#p3830 I thought I would add to this post the model of a remote presenter that we have purchased and have used with ok success. The Zionworx product could do with the option to remap the keyboard though - maybe CTRL+N is a better choice for New Song than F5 (which in Windows means Go To, Refresh or Start Presentation).
Taking into account the previous, and that posted on the included link, the
Kensington Si600 remote presenter works well with Zionworx and can do a distance of 20 metres.