There's a "Battery upgrade" malware out there on the loose which is an app that pretends to be like JuiceDefender (legitimate app) but what it actually does is steals your phone number, IMEI, email address and other information. The app itself is going by the name of "Battery Doctor" or "Battery Upgrade" and can be found shown in paid ads in Admob or potentially other AD services as well.
If you do encounter this app, please do NOT download it or you will have to suffer the consequences. The app itself is not directly available in the Android market but instead makes use of the "unknown sources" checkbox in the Android application settings page to entice the user to install the APK which will then lead to the malware being installed.
Complete details on the malware can be found in the source link below:
Source: Android Community