Another option is too install these checks on the server that is to be monitored. Then create a user that on that server for these checks and setup ssh keys. You can then wrap these checks inside
check_by_ssh. What happens then is Nagios user will ssh into the monitored server, execute the command, and the log out.
For example, the nagios command configuration would look something like:
command_line $USER1$/check_by_ssh -t $_HOSTPARAM_SSH_TIMEOUT$ -H $HOSTADDRESS$ -C "$USER1$/check_procs $ARG1$"
One downside to keep in mind is that ssh has more overhead than other options. However this not really a problem for smaller environments monitoring servers that are not too tight on resources.