What are some alternatives?
When comparing ReadyNAS and ngrok, you can also consider the following products
FreeNAS - FreeNAS is a storage operating system strong and robust enough to meet the needs of enterprise level businesses.
Portmap.io - Expose your local PC to Internet from behind firewall and without real IP address
OpenMediaVault - OpenMediaVault is the next generation network attached storage (NAS) solution based on Debian Linux.
Pagekite - Bring your localhost servers on-line.
Rockstor - Rockstor is a free and open source NAS (Network Attached Storage) operating system.
Serveo - Use SSH to expose local servers over the internet and inspect and replay HTTP traffic.