I have tried many Currency Strength Meter - CSM - but this is the one I use regularly, very easy to read, can be on every chart.

Don't put too much faith in it before about the first hour after London open, if you are able to watch it from daily open, you will see a pair move from the bottom right up to the top within a few bars so it is sensitive.

Basically, I use it as confirmation when a pair is on my radar, not as an entry signal.

http://www.forexfactory.com/showthread.php?p=9389376#post9389376