Whenever you leave an iOS device unattended, it's recommended that Guided Access is activated to stop passersby from closing the Responster app. Guided Access mode will prevent the home and power buttons from functioning (and thus closing the Responster survey you're displaying) unless a code that you've set is entered.
First, you'll need to set up Guided Access:
Step 1) On your iPhone or iPad, head to Settings > General > Accessibility > Guided Access
Step 2) Toggle the slider next to Guided Access to 'On' (green), then tap 'Passcose Settings'.
Step 3) Tap 'Set Guided Access Code' and input a 4-digit code. It is very important you write down/do not forget this code.
**Once your code is set, head to the Responster app and open up the survey you want to display and lock.
Once the survey is running, triple-tap the Home button of your device to enable Guided Access. To exit Guided Access, you'll have to triple-tap the home button again, then enter the code you set previously.