Display whatsapp widget on mobile only

Site URL: http://kickasspicnics.com

I'm using a widget so that site visitors can whatsapp me directly from the site. Great for mobile, but on desktop it just leads you to a prompt "Looks like you don't have the app for whatsapp installed on your computer" which, isn't ideal. Is there a way to nest the widget's code inside some other code so that it's only visible on mobile?

What is access password?