There should be a good way to introspect the running state of the mojo and service manager subsystem(s), including but not limited to:

 * What services exist across the system and what is their current state.
 * What interfaces and methods are exposed or could be bound by each service.
 * What process the services are residing in and what kind of sandbox each service runs in.

Optionally the following would also be useful:

 * IPCs sent across each service/method, to see which ones are being used most.
 * System health data such as latency for IPCs, and whether any services have been restarted or crashed.

Since a lot of this involves running state, perhaps a chrome://mojo-internals or other webui page would be a good way to accomplish this.