A real estate lead is only useful if somebody talks to it. Calltend built a distributed calling service around that awkward little job - and made recruiting callers part of the product.
Drift made the blank lead form feel old-fashioned. A billion-dollar valuation, a major acquisition, a security crisis, and a new AI successor show how quickly the sales conversation moved on.
Its SmartChat service pairs AI targeting with human conversation to catch website visitors before they leave. The sales pitch: more qualified enquiries from the traffic you already bought.

Drift made the B2B website answer back, qualify a lead and book the meeting. A decade later, its sunset is a sharp lesson in what software buyers own - and what they merely rent.
Chatfuel rode Telegram, Messenger, Instagram, WhatsApp, and now TikTok without pretending the channel was the business. Its more useful trick was learning when distribution had broken - and rebuilding around the next customer conversation.

Raised around a family farm and trained in venture capital, the Leadbay co-founder is building sales software for the plumber, manufacturer and regional distributor that conventional databases barely see.
Callbook AI is a Y Combinator (S26) startup building AI voice agents that make and take business phone calls in English, Spanish, and Portuguese. Founded by Colombians Diego Avellaneda and Daniel Martinez, it began as a plug-and-play AI phone system for Zoho CRM and has sharpened its focus on automated debt collections and portfolio management across Latin America, handling calls, WhatsApp, SMS, and email from a single platform.
Simple AI is a San Francisco startup building enterprise-ready voice AI agents that handle inbound and outbound B2C phone calls. Its agents answer questions, personalize offers, qualify leads, and close and upsell transactions over the phone - the company says they convert and upsell up to 30% more than trained human reps. Founded in 2024 by former Y Combinator software leads Catheryn Li and Zach Kamran, Simple AI runs on a proprietary voice stack with sub-850ms end-to-end latency and raised $14M in seed funding in February 2026.