Setup

Add the following lines to your settings.py:

INSTALLED_APPS = (
    ...
    'debug_toolbar_mongo',
    ...
)

DEBUG_TOOLBAR_PANELS = (
    ...
    'debug_toolbar_mongo.panel.MongoDebugPanel',
    ...
)

An extra panel titled "MongoDB" should appear in your debug toolbar.

Note that this should work with any Django application that uses PyMongo.

Obtaining stack traces can slow down queries significantly. To turn them off add the following lines to your settings.py:

DEBUG_TOOLBAR_MONGO_STACKTRACES = False

Disclaimer: only tested in latest Chrome, may fall to pieces in other browers. If you feel like fixing it, contributions are welcome!