Telematic services, such as General Motor's OnStar, will soon grow by one more competitor: In-Drive. But this "connected vehicle service" isn't offered as just a convenience option for a particular brand of cars. Instead, it's an in-car service that might help you save money—if you have a car insurance policy from State Farm Insurance.

The In-Drive service, a joint effort with Hughes Telematics, is like a mash-up of OnStar's aftermarket offering and Progressive Insurance's Snapshot. A small device plugs into the diagnostic port of any car made after 1995 and a communication device can be attached to the car's visor. Together, the add-ons allow drivers to access emergency roadside assistance, vehicle diagnostics, and maintenance reminders.

While it doesn't offer in-vehicle navigation or mobile phone calling, the In-Drive pricing seems attractive. Service is free—after a $10 activation fee—for the first six months. After that, monthly fees are just $5 to $15, depending on the type of services desired.

However, if In-Drive subscribers opt-in to link the service to State Farm's Drive Safe & Save vehicle insurance program, they may save roughly 10 percent on liability, medical payments, collision, and comprehensive coverages. And according to State Farm's press release, "the discount may increase up to 50 percent." The catch: State Farm accesses In-Drive data—vehicle mileage, speed, and braking performance—to determine when and how policy holders drive.

In a recent Consumer Reports report on how to save on car insurance, we noted that such programs have their advantages—and disadvantages. (See: Take advantage of discounts.) A similar program offered by Progressive, for example, found that drivers could save up to 30 percent—if they drive less than national average mileage (about 12,000 miles annually), avoid operation from midnight to 4 a.m., and don't stomp on the brake pedal. But if the data collected show that you're a risk-taker behind the wheel, your insurance rates could go up by as much as 9 percent in some states.

State Farm's In-Drive service debuts in Illinois in September, with more states to be added in 2012.

State Farm Announces New Effort to Bring Connected Vehicle Services and Savings Program to Millions of Drivers [State Farm Insurance]
State Farm Launches OnStar Competitor: In-Drive [Car Connection Blog]
State Farm competing with OnStar's emergency response [CNet]