DES MOINES -- U.S. Rep. Jim Nussle called Tuesday for using satellite technology to constantly track the movements of every registered sex offender in Iowa.

Nussle, a Republican from Manchester who is running for governor, joined a chorus of state leaders who want to use global positioning systems, or GPS, to keep tabs on offenders. But Nussle's plan for monitoring all offenders in "real-time" is the broadest proposal offered so far.

He argued that Iowa's law prohibiting offenders whose victims are children from living within 2,000 feet of a school or day care does nothing to keep tabs on offenders' movements. Nussle said his plan would be more effective in protecting children from repeat offenders.

"Where they travel or where they may be lurking is probably more important than just where they live," Nussle said. "If you are a registered sexual predator, if you're a registered sexual offender, you will be monitored."

But state lawmakers and prosecutors immediately questioned the scope and cost of Nussle's idea. More than 6,000 sex offenders are registered in Iowa and 24-hour tracking would cost millions of dollars.

"I think to make sense, it's got to be targeted at the offenders judged to be the highest risk to re-offend," said Senate Democratic Leader Mike Gronstal of Council Bluffs. Gronstal has also called for real-time GPS tracking.

Nussle estimates his plan would carry a start-up cost of $3.5 million to $5 million. But that doesn't count the ongoing cost of monitoring offenders.

An executive with iSECUREtrac, an Omaha-based company that sells GPS tracking equipment to law enforcement in 45 states, said real-time, or "active GPS" trackers cost between $7 and $10 per day, per offender, to operate.

At that rate, tracking 6,000 offenders would cost $15 million to $21 million annually.

David Vana, the company's chief financial officer, said offenders wear an ankle bracelet and small transmitter on a belt clip. The system reports an offenders' whereabouts every 10 seconds and can alert law enforcement if they approach a school or other off-limits area.

"Once they know they're monitored 24-7, the recidivism rate drops dramatically," said Vana, whose company was recently awarded contracts for sex offender monitoring efforts in Florida and Tennessee.

"Let's be clear about this, it doesn't stop crime. But if they're monitored, you'll be alerted sooner than without it," he said.

Iowa already uses a "passive GPS" system to monitor a small number of sex offenders. That system reports on an offender's movements four times daily.

But most offenders subject to electronic monitoring are tracked by a radio transmitter that only records when an offender leaves and returns home. The transmitter reports that information once each day.

The Department of Corrections uses a risk assessment to determine which offenders use passive GPS and which ones get a radio transmitter.

Lawmakers and prosecutors argue that real-time tracking should be reserved for higher risk offenders.

"I'd like to work with the Department of Corrections and have them determine the risk and then also let them determine which electronic bracelet we put on them," said State Rep. Lance Horbach, R-Tama, who chairs a legislative panel overseeing corrections spending.

Scott County Attorney Bill Davis said he's concerned about the time and money it will take to constantly track his county's 309 registered sex offenders.

"I'm sure we have the capabilities but I'm not sure we've got the money," Davis said.

Johnson County Attorney J. Patrick White said full-time monitoring could be an effective tool if it's backed up by adequate resources for long-term supervision.

"I support real investments in monitoring," White said. "Standing alone, I don't think the global positioning does enough."

Contact Todd Dorman at (515) 243-0138 or at todd.dorman@lee.net.