Tools like Litmus Paper
It's easy to find a slew of test papers and strips online. For example, a quick search of Amazon for &quot;test papers&quot; turned up chlorine test strips for pools and sanitation, glucose test strips for diabetes, phenylthiourea genetic-linked taste tests, UV-C dose test cards, lead acetate paper test for $\ce{H2S}$, WBC and nitrite test strips for UTI... You could write a paper on all the test papers available.
Increasingly, medicine is making use of paper tests because of ease of distribution, storage and use, particularly important in rural location and during emergencies.
BTW, you can make a test paper for polarity testing, and for detection of peroxides, by dipping filter paper into a suspension of starch and potassium iodide, $\ce{KI}$, rather than buy it. Dampen and use it as you would a potato to determine the polarity of an electric cell.