The Unattended Service Account Application ID is not specified or has an invalid value.

This error showed up on the Monitoring > Health Analyzer of my SharePoint 2010 VM.   Apparently after using the wizard to create a new farm, you must double back to supply Visio Services with user credentials for remote data connections.
http://social.msdn.microsoft.com/Forums/en-US/sharepoint2010general/thread/559f72a4-d9ca-4004-b5ca-a0fa6dbad51f was a helpful reference on the steps and below are screenshots.

Steps Taken:

1. Open Health Analyzer and view details
2. Manage the Visio Graphics Service (SA) and confirm Application ID is empty.
3. Manage the Secure Store Service (SA) and Generate New Key
4. Create a New Target Application
5. Provide a unique ID, name, and contact email. Select Group Type.
6. Accept default and just click Next
7. Provide a user name for both fields.  I used “DEMOAdmin” as that is the only user on this machine. Click OK.
8. Enter the Target Application ID back on the Visio Graphics Service (SA) page and click OK.
9. Go to the Health Analyzer rule, open it and click Reanalyze Now, then you should be ready to go.

 

 And you are done. :)

Go ahead check the error again and if error exists click on 'Reanalyze now' to allow sharepoint to check error again and hurray warning/error gone.

Regards,

Viral Shah