Accessing Drupal 6 data using Drupal 7 entities I have a project where we have a legacy system built in Drupal 6 that has been heavily customized, with much of the data stored in custom tables.  We are currently planning a D6 to D7 upgrade, but we have an immediate need to access that data in a Drupal 7 instance, leaving the D6 site intact for now.  

I would like to access that data using Drupal Entities and wrap each D6 table in a Drupal 7 Entity; however I'm having trouble making that work since the underlying assumption with the Entity API is that the data is stored in the local database, and this database is remote.  We can access the database directly from the Drupal 7 instance, and I have the database credentials loaded in settings.php.  I can query the data using Database::getConnection('default', 'legacy')->select(), so I know my connection is good; however I have no idea how to go about structuring an Entity class so that I can leverage EFQ, Views, etc. on this data.

I looked at Remote Entity API, but I"m not dealing with a RESTful service here, I have a direct connection to the D6 database.

Any assistance or hints would be greatly appreciated.  I've worn Google out.
As I understand it you're discounting the Remote Entity API module because you don't have a RESTful service...
The module actually relies on the Web Service Clients module, which provides that REST service for you:

Parallel to the Services module, the Clients module provides the ability to implement pluggable clients to external web services, including external Drupal sites running the Services module, the main use case being connecting to other Drupal installs via the Services module with either the REST or XMLRPC server.
Clients module allows you to create connections to remote services with an admin UI. These handle fetching a result from a remote service. Different types of connection are provided for different types of services. There is a Drupal client connection type for different versions of Services (5.x-0.92, 6.x-2.x, 7.x-3.x), hence Clients can be used to connect to sites with different versions of Drupal.

Emphasis mine.