Peter, Tom-
I have a datasource ready to go for Cisco serial numbers. Tom, it works exactly like you proposed: an instance value is learned from the device and then written to a host property. Once it is a property, we can put it in a report. I have to check about posting procedure within the community, but message me directly and I'll send it to you.
I've also got a request in to enhance the ability for reports to be used for inventory. I think the killer feature is that LM can learn what a device actually has, versus what it supposedly has, as tracked in a asset system. Getting this info in a single report would allow LM to be used to corroborate the asset tracking system. Would be amazing to integrate directly with an asset tool, but a report is an OK start.
By now you guys have realized- Device Inventory Report lets you do host/system.properties but not learned instance values (like serial numbers). Metric Trends Report lets you do the instance values, but not the properties. I want a report that is flexible enough to do both.