I think it would be good to add a Zabbix Internal item to get the Host Maintenance Status. Something very similar to the property maintenance_status of the Host Object in the API.
zabbix[host,maintenance] - Effective maintenance status.
Possible values are:
0 - (default) no maintenance;
1 - maintenance in effect.
I use a lot of Aggregate Checks and I need this item to change my thresholds based on the number of hosts in the group that are in maintenance.