An app which can notify when any of my contacts are online in whatapps

[dragonlore.remo]

Is there any app available which can notify when any of my contacts are online (online only not last seen) in whatapps???

Or Is there a possibility to develop an app to accomplish the same said above??

 

[leeshor]

Hangouts should be able to let you know but those people would also need to be on Hangouts.