If you have keyloggers or malicious apps on your device then none of the apps you have is secure. But if you worry about security of the eSteem, your keys are safe and only stored on your device, they never leave your device. Project is opensource and you can audit source code if you want as well. There is PIN settings which can give you extra security if you worry about loosing your phone or someone else has access to your phone. Hope it helps to clarify some points/concerns.