nagios ALL= NOPASSWD:/usr/lib/nagios/plugins/icinga_check_barman_pg1
in the nrpe.cfg
# check barman on pg1
command[check_barman_pg1]=sudo /usr/lib/nagios/plugins/./icinga_check_barman_pg1
define a service on Icinga like this
check_command check_nrpe_1arg!check_barman_pg1
At present NRPE 2.15 with command args was disabled because considered a security risk.