Hi I have been using dynamic crm for over a decade but relatively new to the android domain, 

Trying to build a custom app which can fetch , create and update data in dynamic crm.

CRM Version : CRM 2015 (On Premise)

Can any one please help on the following 

Are there pre existing business services in dyanamic crm - 

how can they be called from from an android devise using an android sdk

Please advise