I am trying to monitor calls from an app to my server just like Firebug does. I could not find a way to see that in iOS Simulator or in xCode.
Is there a way to do that without sniffing all the traffic? If no, what tool would you suggest?
Personally, I use Charles for that kind of stuff.
When enabled, it will monitor every network request, displaying extended request details, including support for SSL and various request/reponse format, like JSON, etc...
You can also configure it to sniff only requests to specific servers, not the whole traffic.
It's commercial software, but there is a trial, and IMHO it's definitively a great tool.