From Observium

Make sure the hostname Observium uses matches the hostname that Smokeping uses:

+ sw1.hex
 host = sw1.hex

Similarly the hostname used by Slaves should match the hostname used in Observium.

Hosts shouldn't be arranged in any groups or hierarchy.

Set $config['smokeping']['dir'] to the correct directory:

$config['smokeping']['dir']     = "/var/lib/smokeping/";

You should now see a smokeping tab on each pinged device, and each Smokeping server.