recommendations for personal attack alarms?

[nevergoogle]

for lone worker. any that are better than others?

Some self defence teachers don't recommend them as they think the alarm could be used against you, likewise anything you might use as a weapon eg knife, keys, etc. They often suggest shouting/screaming 'Fire!' instead. That only helps if there are people nearby. Obviously, get more opinions before deciding, but thought it should be mentioned that not everybody rates them.

It is best to call out instructions like call the police.