Disabling screen

Hi, how can I disable the screen on a PDA? We've got a navigation application that we use in car with customers, but they keep prodding the screen while they're driving. Is there any way that once we've loaded up the app, we can disable the screen and get it to come back by, say, pressing one of the buttons three times?

[Charlie]

Welcome to our forums.
Try Screenoff. You can get it @ http://www.pocketgear.com/software_detail.asp?id=14498 .
Only problem is it turns the screen off completley but you can still hear the voice commands.

[Stevie]

There is a program that i use called screen off from http://www.handango.com i use it when on the bike to save power and so i can use the programs that i want.

Thanks: I've come across these, but would really like to leave the maps displayed, rather just turn off the overlay. I guess it might need some bespke programming: any ideas on a good (cheap!) bunch?

[Charlie]

Afraid not...sorry!