If you are running Windows Mobile you can use DringMoi to find your misplaced device even if it is on Silent mode and Windows Phone 7 is rumored to have several options for recovering your lost device – like the option to Ring It – but if you are an Android user, you might want to take a look at this if you frequently misplace your device.
WheresMyCellPhone is both an application and a service which helps people find their devices by making them ring. Yeah, what if it’s on Silent? Well, the corresponding application to the website will allow the user to turn the ringer on only for calls received from the website. What’s even better is that the service is free and you can find it in the Market.
(Via: XDA Developers)