Hi Ralph,
The easiest way that I can think of, of doing this would be to use the custom view like Tracy Barkley mentioned, and a group based off of it... then you could write a program that consumes the Afaria APIs to check the members of the group and delete the devices. There are API guides which can help you if you choose this path, and we're always here to help. It's simpler to use a .NET language to consume the APIs, but it is possible to use non .NET languages as well.
How to delete devices using the API:
How to get a list of devices that are in a group:
Afaria APIs getting started guide (there are several in the series):
https://wiki.scn.sap.com/wiki/display/SAPMOB/Server+API+Training+and+How-To+Guides
How to use non .NET languages (primary barrier is the authentication type) is also at the above link in an article titled "SAP Afaria API 301 - Session-less Binding, Basic Authentication and Consuming the Afaria API through SOAP".
Thanks,
John
note: You could technically do this without creating a group, but it is simpler to consume the data returned by the API when getting group members than when running a view.