Lishtot’s device, the TestDrop Pro is able to detect and indicate likely contamination, by a wide range of undesirable materials. The Test Drop Pro is a key fob sized device, that is battery powered and inexpensive.
The Test Drop Pro can not be used to provide certainty that water is safe to drink, but used correctly, it provides a strong indication of the likelihood of contamination by many common materials that are causes for concern. A partial list of tested contaminants is at https://www.lishtot.com/ListOfDetectableContaminants.pdf .
The Lishtot technology is based on the triboelectric phenomenon, which is outlined at length at https://www.lishtot.com/tech.htm