If you’re a nervous or cautious traveler, you might want to check out the eAlarm from BASU. According to the website, it can be used as a crime deterrent, animal repellent (they claim 81% of bears were repelled) and as a rescue signal.
What I like about it is that it’s small (2.79″ x 1.22″ x 0.51″), lightweight (less than one ounce), loud (120dB), reusable, inexpensive ($15.99), and TSA-approved so it can be taken onto planes, as opposed to small weapons such as pepper spray and knives.
What I don’t like about it is that it doesn’t work in temperatures below 14ºF/10ºC or above 104ºF/40ºC and the two sealed CR1632 coin-cell batteries are not replaceable. However, they do last for 30 minutes of total alarm use or up to five years, whichever comes first.
Here’s a video on how it works.
They also have a short endorsement video by Olympic swimmer Ryan Lochte.