A full-featured Android app enables access to all account functions on the go. You should save the KeyStore file to an offline hard drive, or a flash drive that you do not use online. Your bitcoins are only safe if the private key was generated securely, remains a secret, and—most importantly—is controlled only by YOU! Cons: Bitcoin-only. Here are two examples where users got ripped off by leaving bitcoins in the care of a third party:. Cons: No two-factor authentication.