[vinceguidry]

They do, they typically will ask if you're in duress and you need assistance. You can say 'yes' without tipping the person you're with off. The problem is most people in duress won't think to call the cops.

[tyingq]

It does have risks since the 3 digit dial looks distinctive. Or things like redial that could give it away.

[tata71]

9110000000000 as many times as needed.

[noodlesUK]

Does this actually work on mobiles?

[chenxiaolong]

Yep. Same thing with 1800xx911xx (and so on). I made that mistake as a kid with my parents' old unactivated phone. That's when I learned any mobile phone can call emergency services.