An article has been posted to Mashable summarizing reports that came in over late last week from several sources that Ransomware has begun appearing on Android phones in Russia and the Ukraine. Called Simplelocker, it comes as a "trojan payload" with a file/software your think you want. It does the usual encryption of files and demands a ransom to "unlock" your files.
This is the first ransomware reported to attack Android phones.
According to the Sophos Naked Security Blog, you can remove the malware by rebooting your phone in Safe Mode.
UD does have recommendations for anti-malware/anti-virus software for mobile phones. Lookout Mobile is our recommendation for Android phones.
More information:
Dan Goodin: “WARNING Your phone is locked!” Crypto ransomware makes its debut on Android: The rapid evolution of cryptoware that extorts hefty payments continues. (June 6, 2014, Ars Technica)