A free app for Android, by j4velin.

Delayed Lock is an Android application that enables you to delay the time when you have to enter your password or PIN to unlock your device. This way, you can prevent others from getting access to your personal data.

You can even set it to turn off the screen after a certain number of seconds has passed.

Additionally, there is also an optional notification in the Android status bar and a widget to immediately re-enable the lock screen, and free plugins to automatically keep the device unlocked while at certain locations or to control the lockscreen through the Tasker app.