I don't really see the sense in an electronic tag for this kind of offence or this kind of offender either.
I do see the point in a tag for the type of offenders who commit their crimes at night (so anti-social behaviour, people who get drunk and fight a lot in town centres, burglars, joy riders?).
The tag is monitored by a control centre, it tells a control centre when the offender is not within a certain radius of a device installed inside their home. So if they are not at home after their curfew they would be in breach of bail conditions so they could then go back to prison to serve their sentence. In fact one of the countries largest monitoring operations was at one point in Norwich, in that beautiful building near St Crispins roundabout / the Magdalen Street flyover. No idea whether it is still there (the firm may no longer have a contract, was a decade ago when I knew somebody who worked there).
I think they can be effective, but I struggle to see the rationale behind using tags for somebody like Coulson.
The prisons are simply full. Our population, and our criminal base, has grown faster than our prison capacity. It costs a hell of a lot of money to incarcerate people, so doubt it will change anytime soon.