FreeNAS/FreeBSD: How to access status of ZFS volume from jail?

FreeNAS/FreeBSD: How to access status of ZFS volume from jail?

I am trying to set up NRPE to enable remote Nagios monitoring of a new
FreeNAS 0.91 system. I mostly have this working. I can connect and inquire
about basic information like number of processes, users, etc.
But I can't run zpool list to inquire about the health of the RAIDZ, which
is key to properly monitoring the box.
When I run from the main root account, it works:
[stewlg@bauer] /dev# zpool list
NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT
BigMediaToo 21.8T 1.11T 20.6T 5% 1.00x ONLINE /mnt
But when I run it from within the jail, it does not:
root@NagiosJail:/usr/local/libexec/nagios # zpool list
no pools available
I've read many posts, but I'm just not sure about what exactly it is that
I'm trying to allow the jailed environment to do, so I don't know what to
enable.
Posts like this seem like they may contain the answer: Yet I don't know
quite what to do. Is it /etc/devfs.rules that I need to edit?
System layout, to help with names if anyone has an example for me:
A single ZFS volume at /mnt/BigMediaToo
A single jail called NagiosJail. Its dataset is at
/mnt/BigMediaToo/JailsDataset.