I'm not sure about 2.1 but in 2.2 you can create a customized device inventory report with last boot time in it. I guess it is possible in 2.1 as well.In 2.2 you find it under Report > Report Lanuch Pad > Device > Inventory > Create a new report and ...
In 2.2 go to Monitor > Monitoring Policies and add a Interface Health policy to your devices or port groups that you want to monitor.Port groups can you create under Inventory > Grouping > Port
