This will never be as reliable as going into a doctor having him or her look at your penis/vagina/anus, swab all of them, plus take a urine sample, plus oral swabs; as well as their training and experience.
People need to get over themselves; a sexual health checkup is just as mandatory as a PAP smear, or a prostate examination, blood test prior to giving blood, etc. If you're going to have a "promiscuous" sex life then get tested regularly.
If you're not mature enough to go to a doctor and have them look at your body for your benefit, then you're not mature enough to engage in that kind of life style, and you're putting others at risk.
(No I'm not some prude preaching to you.)