http://en.wikipedia.org/wiki/LucyPhone
This is a service that you use when you want to ring a call centre. You ring the call centre on your mobile, and when they put you on hold you key "**" and the LucyPhone service disconnects you from the call centre but sits on hold for you. As soon as the bank/travel company/service centre person comes back on the line they hear a holding message from LucyPhone asking them to hold while Lucyphone rings you back and connect you. Now, I don't actually believe in it but if that isn't Karma I don't know what is!
This has considerably cheered up a quite mundane Thursday.
p.s. I don't know if the service is available in the UK, but if it is it's free, and if it isn't I'm just happy to know that somewhere this is happening :-)