How about a really LOUD whistle?
Esp. for the ladies. BLOW it when in trouble - this is espically since it is compact and can wear around your neck concealed under say a t-shirt.
When doing research for my book, I found an email written by a college student that had been a victim of one of the most vicious rapists we’ve ever seen in my country. I think he rapped between 60-100 women if memory serves me well.
One of the things that surprised me the most was her description of how she was SO terrified, she tried to scream but the voice just didn’t come out. She also mentioned the whistle, saying she believe maybe she could have used that.
I think that is you are that frozen and terrified, even better than a whistle is having an alarm that will do the screaming for you. Also, it's hard to blow a whistle while fighting someone, or getting hit in the face.
These personal alarms are cheap, loud (120-130 DB) and I think they’d be very valuable in such a situation.
Of course the best thing would be a Glock and putting a couple holes into this bastard, doing a favor to us all, but the alarm (and OC Spray) is still a good idea.
There are several models and they are usually very cheap, which maybe isn’t that good because you want something sturdy that can resist a few impacts by a rapist attempting to destroy the gadget, though most likely he’ll flee as soon as he hears the alarm go off. Rapist do NOT want to attract attention, that’s their greatest fear.
Some models just don’t work because they can be easily turned off.
I think that during such a stressful situation you don’t want buttons either, better to have the alarm attacked to your waist, purse or jacket, and simply have a cord you can pull from, like a parachute.
During self defense classes we learn that motor skill are usually limited, specially when the person isn’t used to fighting and dealing with violence, or when paralyzed by fear. (very personal issue, but it’s better to expect to have limited motor skills)
Pulling a cord should be simple enough, specially with something more bulky to grab, like a keychain light or some sort of small bright colored ball (easier to find the cord in the dark)
I didn’t look much into it, but this is one of the loudest ones I found (130 DB ) and with the best reviews. Also works as a door alarm and luggage/purse alarm for travelers.
Multiuse Personal and Door, Window 130 DB Alarm w/ Flashing Light
DealExtreme also has a few, but they look even cheaper and easier to brake/deactivate.
Amazon doesn’t ship these things to South America ( only books and DVDs... thanks Amazon) so if you find another website with a similar or better product and ships internationally, please let me know.