Whether your sibling trying to expose your secrets to your parents or your girlfriend sneaking out to find your relationship with other girls,Accessing your mobile phone might be the best thing to do.
Messenger Lock and APP Lock are your best option when it comes to protecting particular Apps on Android.Messenger Lock one can only be used to protect WhatsApp whereas APP Lock can be used to protect all kind of Android Apps.
Messenger Lock is a very simple App which can only be used to password protect WhatsApp.Install Messenger Lock via Google Play and when you start the application first time it will display options to set a pattern lock for WhatsApp.
The drawback is,it can not be used to protect other Apps but its very easier configure and can be very effective to protect your privacy.
Its a quiet popular Android App which can be used to protect any Android App installed on your Phone,Including WhatsApp and Games.You can install App Lock from Google Play store.
App lock also supports pattern password and it lists all the Applications installed on your Phone.I can be also used to lock incoming calls.Best way to ensure your privacy on Android.