Cheaters, watch out - your girlfriend's about to go all high-tech Columbo.
Top-selling gadgets include cameras implanted in alarm clocks, e-mail scanning devices, and blacklights designed to find proof of sexual activity in the bedroom.
"If there's anything goin on, a spouse will more than likely make contact with a lover on Valentine's Day, the day before or the day after," relationship expert and author Ruth Houston told USA Today.
Private investigators have their hands full during the lovers' holiday, said Detective Jimmie Mesis, the editor of P.I. magazine. Sales of GPS trackers were 20 percent higher than normal, Mesis said.
Security firms saw a similar bump in business as they peddled spyware to paranoid lovers - sales are up 141 percent this month, BrickHouse Security CEO Todd Morris said.
Morris said he was surprised sales of the expensive equipment - which retails between $50 and $400 - continued to rise even in the dismal economy.
"Apparently," he said, "money troubles don't stop the philandering."