I like the ZTS MBT-1 also. This meter, unlike a volt meter, tests the battery under an immitation load. A volt meter alone will not tell you how much battery life you have left.
Recently, my EDC light has been an LF3XT. LiteFlux incorporates a battery testing feature and gives a fairly accurate voltage readout under the load of the actual brightness level you have your light set at. This feature is also found in the LF5XT. I wish more flashlights incorporated this feature, because out in the field, without carrying a separate battery tester with you, you can be caught by suprise when a battery goes during use since most of our LED lights are regulated and seem to die rather suddenly.