Ok slightly off topic but where better to ask.

I need a piece of fishing line for something other than fishing but require
that it is as thin as possible and doesnt stretch too much. Also something
that wont break too easily.
(It is for an alarm system and will be connected to a pin , so when pulled
out the alarm goes off) To be honest a piece of string would suffice but I
thought fishing line would be more discreet.

I dont know the first thing about breaking strains etc hence the reason for
asking on here.

Any advice appreciated.
thanks