By Rafael Olmeda From South Florida Sun Sentinel FORT LAUDERDALE, Fla.—Alison Kessler told police she was suspicious when her son’s father, John Stacey, seemed to know that she had paid a visit to the courthouse. She didn’t see him following her. How did he know? When a mechanic found a tracking device stuck to the underside of her car, it made sense. Kessler went to the police and accused Stacey of planting it. It would have been that easy. Planting small tracking devices on cars to monitor people’s real-time locations is simple, cheap and, in many cases, illegal, according to lawyers and private investigators in South Florida. The proliferation of tracking devices—particularly the type of popular gadgets being sold to help you find your belongings, such as your wallet, keys or luggage—have led to an increase in fears of stalking, experts say. Five years ago, two Hallandale Beach commissioners and …