Pressure-Activated Buttons

For a slim-line package as the one you are working on the best idea I can suggest would be to use standard low profile tactile switches (for example the one below or similar) which are available from your local component distributor,

http://www.newark.com/omron-electronic-components/b3f-1025/tactile-switch/dp/89C4134

http://www.newark.com/switches

and recess and cover them with a flexible plastic sheet (adhesive plastic film or similar works really well and is quite inexpensive and easy to work with) which forms a cover (and also forms the front of the personal alarm). The force necessary to activate the switches can be controlled by the use of different cover materials and thicknesses as well as the depth of the depression through the cover necessary to activate the tactile switches.

This is a common method of switch control in the industry and I have used exactly the same thing for wall-mounted equipment in harsh rural farm environments (example custom label supplier shown below, although you can order sheets from suppliers or possibly even large office stationary suppliers).

http://www.permark.co.nz/Services/Graphic+Overlay.html

As an added advantage this also adds to the alarms weather resistance by sealing the switches (important for an electronic device worn on the wrist). Two button activation is just as simple with this method by having a plastic or similar partition separating the switches to prevent accidental activation by a single finger or object, but still allowing easy activation of both switches using two fingers on one hand.

Another possible option is the common membrane switch which has the switch element built into the plastic film. This is a bit more difficult to work with and design for a low quantity product run, and so may not be viable for your particular needs (but is worth a look).

http://www.permark.co.nz/Services/Membrane+Keypad.html

http://en.wikipedia.org/wiki/Membrane_switch

Hi thanks for your help. You're so full of knowledge!

I'll look into both options but so far other people I have spoken to also suggest looking at membrane switches!

Weewoo

or this

http://www.who-sells-it.com/r/parker-pressure-switch.html