Phone App
A phone app was first released CRM in version 2013.
It was updated for the Online 2015 Update 1 release.
The same app can be used for CRM 2013 and 2015 On-premise (provided that an Internet-facing Deployment has been configured) and CRM Online.
Th app is available for Windows, Android and Apple phones.
Tablet App
A tablet app was first released for CRM in version 2013 and can be used with CRM 2013 and CRM 2015 On-premise (provided that an Internet-facing Deployment has been configured) and CRM Online.
The app is available for Windows 8, Windows 8.1, Android and iPad. Supported tablets are described here https://technet.microsoft.com/library/dn531131.aspx