Yes, you can sign-in on different devices. You can be logged in to RealAgent and RealAnalytics at the same time. However, do note that only 1 session is permitted at a time for each of the two Apps.
For example, if you login to RealAgent on your mobile device, you will be automatically logged out of your tablet device, if you have installed it on both devices. However, since RealAnalytics is not compatible on mobile devices, it will not log out of your session on your tablet devices unless you login to it on a separate tablet device.
To switch to another device, you would simply have to log in again, that's all!