DataGroomr fully supports deduplication of any object in Salesforce, including any custom object.  Unlike the standard objects (Leads, Contacts and Accounts) there is no pre-trained matching models for custom objects.  However, it is pretty easy to create these models for yourself and then add a dataset that will dedupe your custom object:

  1. Start by adding you custom object in the Matching Models section.   
  2. Then create and train a model for that object.  
  3. Finally create and configure a dataset for your custom object.