Yes! Sling only works on smartphones, we do not have a browser version for the moment (exploring the idea at the moment, get in touch with us if this is something you're interested in). You need a recent smart phone running iOS and Android in order to:
Use the Sling App
Set up a Sling Wallet
Send Sling Links
You do not need a mobile phone in order to redeem a Sling Link for cash in our supported countries.