The new Monster LED brake fluid tester (part no. MST6140A) tests several DOT 3, DOT 4, and DOT 5.1 brake fluids.
KTI Has a New Brake Fluid Tester
K Tool International (KTI) has released a Brake Fluid Tester (part no. KTI70120) that takes one second to test the fluid and automatically shuts off after two seconds.