APIs are a big part of the internet ecosystem today. From Facebook and Twitter to Google and Salesforce, if you name a prominent internet company today, chances are that it offers APIs to its customers and third party developers.

And for good reason: allowing others to create new products and services on top of yours can be a highly effective way to build value.

But while APIs are, for most companies, an add-on, a few companies are based almost entirely on their APIs. One of the most prominent that falls into that category is a company called Twilio, which offers APIs that allow its customers to build voice, VOIP and SMS applications.

With Twilio, a business can offer build a web application that allows its
customers to check the status of an order in real time over the phone.
Or a business could build an application that automatically calls
customers after a purchase to obtain feedback about service quality.

Twilio provides the phone number, and its REST API allows the company’s
application to programatically handle the call.

Previously, Twilio customers were able to use the company’s APIs to make
calls to anywhere in the world, but its inbound services limited
customers to phone numbers in the United States and Canada.

No more.
Yesterday, Twilio hopped the pond and launched its Voice service in the
U.K., and it released public beta offerings in several other
EU markets — France, Poland, Austria, Denmark and Portugal.

In the U.K., inbound calls in the U.K. cost 1 cent per minute, outbound
calls to landlines cost 2 cents per minute and outbound calls to mobile
phones in the U.K. cost 14 cents per minute. A local phone number is
$1/month. Twilio also offers Freephone capabilities for $2/month per
number and at a cost of 6 cents per minute for inbound calls.

In the United States, Twilio is used by companies large and small to
build everything from automated phone reminder services to interactive
voice response (IVR) systems.

Given Twilio’s prominence in the U.S., and the maturity
of its offering (it offers client libraries for popular programming
languages like PHP and Ruby and has an active developer community), the
company’s entry into the U.K. market should be good news for businesses,
entrepreneurs and developers who haven’t forgotten that the telephone
is still a powerful communications tool.