From the December 2003 issue of Entrepreneur

Want to add still more precision to your well-calibrated golf swing? The SD GPS receiver from iGolf Technologies uses GPS technology to measure the distance to the front, center and back of a golf green. Offered through the company's Web site, www.igolftech.com, it includes a distance-off-the-tee calculator, a four-player score card and Mapopolis software, which has point-to-point directions to help you find your way to a new course.

SD GPS is compatible with any PDA with an SDIO slot and is small enough to run off your PDA battery. ($349, MSRP; $299 for Internet pre-orders).