dummy wallets with minimal contents are one solution, there used to be the concept (American I'm afraid) of an amount that the mugger would not beat you up for, out of spite. I had one in Honk Kong with cardboard credit cards. The time I nearly had a wallet grabbed was when buying in a public park and it was the real wallet but muggers don't work that way. I was holding it across the width not the thickness and felt a tug - I must have been wary. She (see later) tugged from the other direction and as I looked around had to do 360 - the dip was in the toilets by then - probably the ladies loo. All well worked-out. Lift cash, pass cards to next cubicle and flush all else away. Not that day.

A personal alrm is always a good thing - for reassurance if not anything else. but you have to wear it so that it can be pulled and thrown. I have one with a light - it doubles as a torch and presumeably flashes if set off. The moment has passed when I needed it (in the work place!) but it was re-assuring. Bugger the image thing.