in my jurisdiction the defendants have to pay a fee for the monitors - a deposit of several hundred dollars and then a daily service fee to be paid at the end of each week.
and there are a limited # of monitors available - if a defendant is released to home monitoring the jail doesn't actually release them unless/until a monitor is available. plus while the defendant is out there w/the monitor cops have to swing by their home and do curfew checks. if they go outside their bounds then a cop has to go check on them immediately.
still, i like the home monitoring programs but i wouldn't want to see ankle monitors used in lieu of cash bond in most cases. i think ankle monitors are more appropriate an alternative to an actual jail sentence.