HP Bladesystem (C7000) Onboard Administrator can report enclosure related hardware issues as SNMP traps. So there are alarms from PSUs, FANs etc.
This does not work with blade's hardware (like faulty server blade disks), however OA is aware of such issues, OA web gui shows them, but there's no SNMP trap sent.
Supervising every single blade via ILO or OS is not convenient option for me. Maybe there's any way to do it via OA? I'm not considering HP Systems Insight Manager (SIM) because of the cost and the fact that I'm using another NMS.
No there's not, you're expected to do it either via each blade's iLO, it's OS or SIM/OpenView.
You can always use their API It's not terribly difficult, you'd just need to write some code.