NEW YORK (MainStreet) — The grainy black and white surveillance video of the abduction of a nursing assistant from a Philadelphia street last week shocked viewers. The swift arrest of a suspect was a surprising relief in a world where so many violent crimes seem to go unsolved. And the manner in which the suspect was located was also a surprise to many of us: a GPS device planted on the alleged perpetrator's car by a cautious lender.

The report brought to light an often surreptitious and perhaps little-known practice of those who cater to so-called "risky" borrowers. Lenders who cater to "sub-prime" customers – those with below-average credit scores, poor payment histories or low-income job histories – have been tracking the whereabouts of customers, often without their knowledge.

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Car dealers and lenders are especially prone to utilize such surveillance measures.

"Like auto dealers, vehicle finance companies are turning to GPS vehicle tracking in order to offer loans to subprime buyers while minimizing their risk," says Spireon, a provider of such devices, in an online promotional piece. "Our easy-to-use tools and services provide the real-time business intelligence lenders need to extend credit to more buyers, as well as increase productivity and efficiency. With [such devices], lenders are able to improve loan portfolio performance and price loans more competitively."

The company provides a host of "less invasive ways" to track a customer's whereabouts – and even "check references" based on the locations customers frequent. The technology can also "forecast reliable collection locations at any given time and day for repossession purposes."

You might guess that these devices are primarily used by the "buy here, pay here," dealers, but David Main, who owns a GPS removal service in Phoenix, says 90% of the dealers in that area install the hidden devices in their vehicles, according to KSAZ Fox 10 News.

Not only can the GPS locate a car, some can disable them, as well. the New York Timesreported just such an incident in September when a Las Vegas woman with a sick child couldn't get her daughter to an emergency room because just such a device prevented her from starting her car.

--Hal M. Bundrick is a Certified Financial Planner and contributor to MainStreet. Follow him on Twitter: @HalMBundrick