There are quite a few services that provide similar features, with the exception of the call button on a web site.

Skype offers call-in and call-out services which provides you with a phone number (your choice of area codes and countries) and the ability to call from your computer to a regular phone. Also provided, is voice mail and call forwarding. The plans available can cost as little as $5 USD per month. With an adapter which costs $40 or so you can connect your current house phones to the system.

There are others out there as well, including SipPhone and Yahoo. Some even offer toll-free numbers with FAX and voice mail capability.

All of these services can forward to any land-line or cellular phone number or voice mail, keeping your personal numbers hidden.

Web hosts as well as other small business's should take advantage of these services to provide their customers with a contact number for use if their site is unavailable.

What do you mean by "safe use via the internet".