APImetrics has announced API.expert. The service gives developers insight into performance for leading APIs. Real-time data is available without any configuration needed. At launch, the service includes weekly data from leading API providers.
There are a number of ways of delivering data in real-time but until recently it has looked like PubSubHubbub, with the backing of Google, was going to be the preferred method. However, the past couple of weeks have seen a couple of interesting developments which could indicate that the developer community may actually prefer HTTP Streaming.