Trojan.Cryptolocker and its imitators have been a major threat in the Windows world for quite some time. Now that same "business model" is beginning to be seen on Mobiles.
Please update your Android's definitions to protect against
Android.Simplocker
http://www.symantec.com/security_response/writeup.jsp?docid=2014-060610-5533-99
Once any files are encrypted, there is no way to recover them. Prevention is far better than any attempted cure!
There is a similar scam being seen with Apple, but that works via "social engineering" rather than a technical means.
Apple IDs Compromised: iPhones, iPads, and Macs Locked, Held for Ransom
https://www-secure.symantec.com/connect/blogs/apple-ids-compromised-iphones-ipads-and-macs-locked-held-ransom
Education is the best defense against these threats, and ensuring that your security product upon the device is up-to-date and functioning correctly.
And, remember: if you do fall victim, don't pay the ransom. It just provides R&D money for the authors to develop a new and better way to attack you.
Hope this helps!
Mick