^
Does it have to be an official bodyguarding profession and the H/h strangers to begin with?
Because if you're willing to go with former one-night stand encountered detective blackmailed by protective father, who winds up embarking with a relationship with the heroine unaware he's also secretly protecting her from a stalker, we recently received this freebie from Entangled:
A Night of Southern Comfort, which you may wish to try, though the reviews look kind of mixed.