My wife and I have purchased I Password for our computers and it works fine. My wife and I have the same Samsung 4G phones, probably about 3 years old.
My phone has firmware version 2.2.1. My wife's Phone has firmware version 2.3.6.
Two years ago I successfully installed the 1 Password app from the Google Play Store on to my phone. However, recently when I try to download the same app on to my wife's phone, the Play Store App tells me that her "device is not compatible with this version."