Use production App Engine datastore on development machine?
TL;DR: We do not support having the dev_appserver use the real app-engine datastore.  Even with the suggested use of "remote_api", AFAIK, the dev_appserver does not know how to use it.
If you really want to make this work, you could write your own low-level API and have your own datastore abstraction that uses your API instead of the actual datastore, however this is a non trivial amount of work.
Another option is to have a servlet that can pre-populate your dev datastore with the data you need from checked in files.  The checked in raw data could be non-real data or obfuscated real data.  At dev_appserver startup, you hit this URL and your database becomes pre-populated with data. If you take this route, you get the bonus of not operating on your live data with dev code.
HTH!
Is it possible to setup the App Engine SDK on my local machine to use the live datastore while developing?  Sometimes it's just easier for my workflow to work live.  
If not, is there an easy way to download or sync the live data to development machine?
Thanks!