You need to create UDP check out this video will help .
You need the OID number for the both devices and can publish on the Node details page as gauge .
Let me know if this helps, or if you require any further information.
The NPM in Engineer's Toolset does not do custom polling. You can use the SNMP Real TIme Graph and type in your OID for the temperature manually. Alternatively you can check out the Network Device Monitor free tool to set up a custom poller. I recommend you look into our Orion NPM product. It is designed to do custom polling in a very friendly way.