On the CLI, is there a command to find out how much power the router is using?
My understanding is that the availability of specific environmental monitoring characteristics depends not only on software, but also on the availability of specific 'sensors' on each hardware platform. I guess it is more possible to have more support in higher-end platforms than lower-end for such environmental indicators, since those are more expensive, critical and consume more resources. The output you can get from "sh environment" options will be different in different platforms. The following document covers platforms that you haven't mentioned, but you can get the idea:
Now, I am not doubting anyone here, but since you expressed interest in other platforms as well besides the 2800 (and if you are indeed very stubborn ), maybe you could explore SNMP MIBs as well and see what you get. I am saying this because sometimes some information not available from CLI might be available from SNMP variables and vice versa. To be noted though that I am not sure if this applies to this specific case or you will end up with the same information you get from CLI (since information is hardware dependent).
From a fast search I found the following threads in Network Management (under Network Infrastructure) section of NetPro:
So, maybe you could ask there and get answers for any specific hardware you are interested in either using CLI or SNMP. As an author of this thread you have the option to 'move thread' in Network Management section using Actions sidebar box on the top right of your thread. You can also edit the subject line or just post an update specifically stating which platforms you are interested in and/or edit the tags of your thread.