Noizer - Ambient sounds like Noisli, but free
Stealthy: Secret Messenger - Chat anonymously with friends & strangers
Defonic - Create a unique sound environment at home or in the office
Vuash - Send secret messages safely.
Noisli - Noisli is a fantastic background noise and color generator for working and relaxing. Online soothing ambient sounds like White noise, Rain and Coffee Shop.
Phonebot - Make phone calls from within a Slack channel