Multiple site bridging logins

Wouldn’t it be cool if you could set up a service like PayPal to track you across certain sites with certain trigger behaviours and then perform a certain action. 

So, for example, if you clicked the ‘donate’ button on and logged-in to Facebook, and then clicked through to PayPal within thirty seconds, PayPal would recognise your journey and automatically log you in. 

It would be like IFTTT across multiple sites and could be used to speed up multiple site journeys that you do regularly.