Say you want to read your email.  But you are at an internet café and the paranoid version of you wonders if there is a keylogger on the machine.

Wouldn’t it be nice to get a temporary password.

Say you use gmail.  So you open your phone.  Surf to temppwd.google.com and log in as you usually do.  Back you get a temp password that is valid for 1 minute.
Now surf to gmail at the café computer and use your temp password.

A variant of this is to have your tablet at home logging in to your email and then change the password at work. The tablet keeps logging in with the old password and your account gets locked.

This happened to me with my VPN connection and secureid.

Maybe a solution is to have several usr (probably with different pwd) to the same account. For instance a usr for public machines which you can lock without affecting you other pwds you use at work or home.

Say I get an idea I want to publish on my site.  This very site for instance.
Also say I am at a friend’s place and my computer is at home so I have to borrow my friend’s computer.

My password is of course 40 ch4R4ct!ers-long and impossible to remember.  Or at least very hard to remember.  Opening Keepass at my phone and copying character by ch4r4ct!er is boring and error prone.

Wouldn’t it be nice to somehow magically copy the password (or temporary password even) from my phone to his computer.  I haven’t figured out how to connect my phone and his machine and authenticate and authorize and do the copying and all other stuff that is involved but the idea is nice.

This could be taken further.  Why talk about a friend’s machine?  Some work places, typically point of sales, have a card you have to insert into the machine or a magnet to attach to interact with the computer.  I have seen ads for a RFID tag? which you have in your pocket; leave he desk and the computer notices you have left and locks.  One could use the all present mobile phone for the same stunt