AVG Mobilation Anti-Virus Free 1.2.5
the author of this app says:
Fast and lightweight malicious app protection for your phone. Antivirus Free will detect new applications that are installed on your system, and cross-reference them with our database of known malicious apps. It uses less than 0.1% of your battery, and will let you know when such an app is detected, keeping your phone secure.
Android 1.6 or higher.