if it's dumb switch maybe you can ping something attached behind it. there are devices like pingers but you don't even need to buy them. get some old adsl router, turn off dhcp in it, give it static ip address and use nagios to check if the device responds to ping. if not - probably router or a switch hanged.
One thing you can do is look for SNMP libraries for said switches. But given the fact that they're unmanaged, I think your only option might be to perform a pingtest and that's it.
if it's dumb switch maybe you can ping something attached behind it. there are devices like pingers but you don't even need to buy them. get some old adsl router, turn off dhcp in it, give it static ip address and use nagios to check if the device responds to ping. if not - probably router or a switch hanged.
One thing you can do is look for SNMP libraries for said switches. But given the fact that they're unmanaged, I think your only option might be to perform a pingtest and that's it.
What brand / type are they ?