nrpe is nice, but if you plan on having a huge nagios site someday, then start now by making most of your checks passive checks. The central nagios server will not actually make the check, it will only have to read the results of the check, sent to it by the remote check. A distributed server, using nsca, or any other way possible, make it passive.
Even if you can’t ping the device, there must be someway to get the info to nagios. Have it emailed, parse the info with a cronjob, then post it to the nagios.cmd file, whatever it takes, the info should be able to be displayed.