The only "viruses" that have been discovered so far could barely be considered such, privacy concerns perhaps, but mostly it is the Anti-Virus companies that are pushing the "LOOK VIRUSES OFMG!!" mentality.
They android permission system for apps is sufficient currently if you actually look at them and make prudent decisions based on them; Wallpaper app asking for GPS settings, thats an uninstall/report. Wallpaper has no business knowing where I am (unless it is a live map wallpaper?)
Ultimately I'm not going to bother with the antivirus stuff until I see some hard evidence of true viruses, which I would consider the sort that can secretly root your phone, and gain permission to anything all while masquerading as a normal app with all the appropriate permissions for the "dummy" app.
That is possible now but I haven't heard of it happen, nor do I think any of these antivirus softwares can even protect against that, (hell with root the virus could just delete them)
What can you do against an app with more system permissions than the virus software? not much.
