In our environment, we use Zenoss for monitoring. Since Zenoss primarliy uses SNMP and WMI to communicate with the monitored devices, it is basically agentless. Zenoss can also use any Nagios style plugins, which opens up the entire Nagios universe of tools. We have created a webservices interface that allows Zenoss to automatically create, update, and close Footprints issues based on whether an alert has been created or cleared. We have also created an interface using ODBC and webservices that allows us to import our entire Zenoss configuration into the Footprints CMDB.
Zenoss has a free version of the software available at http://community.zenoss.org. There is a large and active user community supporting the community version. There is also an enterprise version available if you wish to have paid support. http://www.zenoss.com
There is a lightweight event console tailored for iPhone usage at http://sourceforge.net/projects/zipec/