The HP LogicDart

A logic test device somewhere between a logic probe and a logic analyzer, this is a piece of test equipment that crosses HP's calculator expertise with their test equipment capabilities. Introduced in 1998, it came a little after its time and didn't really meet its market.

However, if you are troubleshooting digital logic, it is a useful handheld tool.

It has five functions

 - DC Voltmeter: low voltages only, nothing special
 - Frequency meter
 - Resistance, continuity and diode test
 - Logic probe. Bright red lights.
 - 3-channel logic analyzer

These are all useful functions for poking around a board. The first four are basic test. This can mostly be done with a scope, but the handheld form factor is more convenient.

The Agilent page with manual and datasheet.

Evaluation engineering on the LogicDart test program and user feedback.