BRAND:ZHANGQIYING
This is one of those things that you hope you never need.
But its small enough and cheap enough to get anyway.
Its an extra loud whistle that you can carry with you at all times and use in the (hopefully unlikely) event that you need to summon help.
Youve doubtless seen TV shows where people call for help but you also know that, sooner or later, your voice would go if you had to yell for help for any length of time. Plus there are lots of places where a voice wouldnt carry far enough for people to hear you.
But so long as you can puff into this whistle, youll be able to attract attention from anyone within ear shot - which, because its a whistle, will probably be further than your voice would carry.
If you know any morse code, you could even send a message. The easiest message to remember would be the international SOS distress signal - a continuous sequence of three dots (short blasts), three dashes (long blasts) and three dots (short blasts again). Its instantly recognisable and will attract the attention of anyone who can hear it. Theyll be able to use it to locate you and come to your rescue.
Ive not got anything to measure the decibel level this gives out but can definitely attest to it being loud!