Google already does this with GMail. Scroll down to the bottom and it's in the lower right corner. Facebook also provides access to all recent/active sessions

Google already does this with GMail. Scroll down to the bottom and it's in the lower right corner. Facebook also provides access to all recent/active sessions and their last accessed time under Settings -> Security. They've got all kinds of other good security features that are worth enabling too. I suspect a better long-term approach here is going to be something like Mozilla Persona (with the option of easily using your own domain for auth & auth if you like). Then the service doesn't have your password. They could still give the Feds access to your data, but at least the Feds won't be able to leverage your password against other services (greater adoption of password managers would also help this scenario). And of course, enable two-factor auth on any site that supports it.