On clicking a button i want to instruct an app whether to start or stop sendind data on thingworx dashboard.

Hi Anupriya Agarwal​ , This can be achieved by creating a service which will change the value of  dataChangeType.

dataChangeType : The data change type describes how the ThingWorx server responds when the value in the RemoteThing on the server changes.

Subscriptions to these value changes can be created on the server. If nothing needs to react to

the property change, it is recommended that this value be set to NEVER.

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Value Description:

ALWAYS :  Always notify of the value change even if the same value comes in multiple times in a row

VALUE  : Notify only if the value changes

ON     :For BOOLEAN types, notify only if the value is true.

OFF    :For BOOLEAN types notify only if the value is false.

NEVER  :The server should do nothing based on the value change.

So I believe you want from the Platform to be able to send a command to the mobile so that it starts and stops sending data.

You will need a 'service' on the mobile device that is then mapped so it can be invoked by a Remote Service on the platform.

You could do it also by using a specific property that can be set from both the Mobile or Platform and have the mobile check that value during its cycles. (this would mean there is a delayed response)