Wixey recently introduced the WR2000 Digital Height Gauge, which allows you to dial in tablesaw-blade and router-bit heights to within 0.001 of an inch.
Wixey gauge

One of the pioneers of digital devices in woodworking, Wixey goes one step further with its WR2000 Digital Height Gauge. This tool is attached to a magnetic base that's sure to hold in place on cast-iron tabletops while you adjust your blade or bit height. And it works just was well on non-metallic surfaces.

The WR2000 provides you with three forms of LCD resolution: fractions (to 164 ) and decimals (to 0.001) in inches, and millimeters (to 0.05). The gauge will measure up to 414 inches tall. As with all Wixey products, it has an automatic shutoff feature to save battery life.

You can buy the WR2000 for $60 online at wixey.com or at numerous woodworking suppliers around the country.