VSTS can post messages to your flow in Flowdock so everyone will know when code has been pushed or checked in, a build has finished, or a work item has been created or updated.
Set up a flow
If you don't have a Flowdock account, get one here.
In Flowdock, add a flow.
Create the flow.
Configure the flow.
Go to the flow's administration page.
Get the API token.
Use a service hook to push messages
In VSTS, open your team project's administration page.
Add a service hook.
Configure the VSTS event that will push a message to Flowdock.
Tell Flowdock what action to take.
Test the service hook subscription and finish the wizard.
Now messages will be posted to your flow in Flowdock.
VSTS doesn't charge for the framework for integrating with external services. Check out the specific service's site for pricing related to their services.
Q & A
Q: Can I programmatically create subscriptions?
A: Yes, see details here.
Q: Where can I get more information about Flowdock?
A: At flowdock.com.