Greetings! The URL API would not be suited for the type of application you are looking to build; it's probable that the XML API would not suffice either. Both are meant to automate tasks such as logging in, creating users, scheduling and joining meetings, and static reporting.
You can take a look at the sample code for lstmeetingattendeeHistory on the XML API website to get an idea of what kind of information can be returned. Meeting room passwords are not needed, the API will return a list of meetings which the API user (the webExID listed in <securitycontext>) owns, unless the API user is a site admin, in which case info for all meetings is returned.
Cisco DevNet: WebEx Conferencing - XML API - XML API Reference