Twilio is a company that offers an Internet API so companies can create Web applications that make or take phone calls. For website application developers, getting any sort of connection to telephones can be a show-stopper. Wireless carriers, which are enormous bureaucracies, can take forever to approve and support the connection. Twilio was founded in 2007 to solve that problem at an affordable price. Twilio offers Web app makers an API connection to phone service, for which Twilio already has the hookup to phone service. Twilio will sell your company one or more phone numbers that are already live and ready to take or make calls.

High-profile customers include the Democratic National Committee, which hands out advocacy apps that connect constituents to their elected officials’ phone lines. The Ground Zero Museum lets people call in and leave spoken remembrances that will be playable at the museum when it is completed. But of course the biggest target for Twilio is brand marketers. Fans of the band Lamb of God, for example, can order a pre-recorded phone call from drummer Chris Adler via the band’s website.

Today, Twilio announced that they now have an SMS interface to their API, too. It’s already been stress-tested at a recent Salesforce.com conference, where attendees could text in the booth number of their favorite exhibitor to a people’s-choice contest. Early-stage mobile payments service Venmo is using Twilio for payments via text: “Send $5 to Stupify.com.”

The company also announced that it has lowered its prices for all past, present and future customers. Phone numbers have been knocked down from $5 per month apiece — really, that’s practically free for a business-enabling Web-to-phone connection — to $2 for toll-free numbers and $1 per month for local numbers in the United States. Many clients buy only one number, but online retailers sometimes rent thousands of numbers. They place a different number in each Web ad they serve. That way, when a customer dials a call center to order a product, the vendor knows which ad reeled that buyer in.

Twilio, a San Francisco startup, has received several million dollars in funding in two rounds. The most recent, a Series A second round in December, totaled $3.7 million from Union Square Ventures, the Founders Fund, angel Mitch Kapor and several others.