@ayounsi has proposed netbox, for an IPAM and Racktables replacement. It's a Django app, written by DigitalOcean and looks really promising. It seems to have more features than servermon and given our minimal time investment into servermon, it looks more likely that this will be both more sustainable and cover more use cases than the ones we were thinking already.
Since v2, it also supports a fully read/write REST API, which will certainly come in useful in a few different ways (e.g. polling a server's location from Puppet, pulling IPAM data in netops' configuration management, potentially integrating with our hardware provisioning workflows etc.).
@ayounsi has set up a test instance in Labs already. We should evaluate it further and attempt to script a data migration, to see if everything we are planning to do with it can be done. T150651, originally worked on by @akosiaris for servermon, will probably be an issue here too.