I guess nobody will buy crypto-related (and very likely closed-source) apps because of security reasons. It is pretty easy to integrate a spying software or key logger.
Well if the app will be made for the app store then i doubt there will be any spyware.
I am saying this because apple has very strict rules and does not approve these kind of apps.
So there is no chance for any viruses or spyware, and about google play there are only few hours to few days that an app can be in their market.