A free app for Android, by Unique Solution.

This is an excellent application for anyone who is looking to get information about their mobile device. It provides the following functions:

Find the IMEI number of the device, which is a unique number that is used by a GSM network, WCDMA, and IDEN mobile phones to identify valid devices and provide specific services to such mobiles phones. Check the device network info, software, and hardware information about your smart phone. See the build serial, Memory info, Battery info, and network info. Copy the device info and IMEI to the clipboard or share to your email address for future reference in case your mobile gets lost or stolen.