Hi,
I believe what you're looking for is a wireless mouse that is used "in mid
air" (ie. as opposed to needing a desktop surface).

As you may have found already, using your regular desktop mouse, if you
start a slideshow and move the mouse around, the Windows pointer will appear
over your slideshow.  If I've understood your need correctly you are trying
to emulate this feature, but using a "mid air" mouse.

Here are two suggestions that basically depend on your budget:

LOW BUDGET:  Use a wireless mouse with a "hand held mat".  Yes, it's a
kludge, but it's cheap :-)

HIGH BUDGET:  There are "gyro" mice around that allow a presenter to walk
around and use the mouse without a desktop.  Gyration has been making these
things for years, but they're darned expensive!  You should do a proper
Google search to see if there are cheaper alternatives.

http://www.gyration.com/p-55-go-pro-24ghz-gyrotransport-air-mouse-presenter-512m
b.aspx

Cheers,
Geoff

use an ordinary mouse, the mouse pointer will appear on the slideshow
screen.