Though only two-and-a-half years old and in the midst of raising its second tranche of finance, the company has already picked up such clients as Barclays Bank, Legal & General, PowerGen, KPMG and even the online service provider CompuServe. Interest is mounting around the world and a business that until recently was based in a loft of a private house on the south coast is planning to open offices in Germany and the United States shortly.
The idea behind the service is very simple, insists Eric van der Kleij, RealCall's co-founder and chief operating officer. Essentially, a "button" creates a link between the internet and telecommunications and is provided free to a website owner, which then pays upfront for a certain amount of use - rather like a phonecard user.
The service, which is applicable to digital television as well as the internet, works by means of four simple steps. First, the web user wanting to respond to a company presses the button on a we site or online advertisement. Then, the RealCall technology processes the request and carries out security checks before sending the advertiser an automated call with the user's name and telephone number. Finally, the idea is, the advertiser calls the user back.
The benefit to the company is that visitors to the website - whether customers looking to buy products or people just generally seeking information - have a means of obtaining feedback. As Mr van der Kleij says, "it puts the human touch back" by demonstrating firms are willing to talk to their customers.
But with orders for the buttons already in their millions, Mr van der Kleij also admits that he cannot anticipate how every customer will use the service. KPMG, for example, had surprised him by using it for graduate recruitment purposes. Would-be job candidates take part in a psychological assessment test and, if they pass, can use the button to leave their contact details.
Many of the organisations that have so far taken up the service - which charges call-backs at a fixed rate of 35p each - are, understandably, large. But Mr van der Kleij sees opportunities for small and medium-sized enterprises, too. RealCall has, for example, linked up with Livetown Online Media to enable businesses in Glasgow to obtain business directly from the internet even if they do not own a computer. Mr van der Kleij says it "connects the internet to the `internotyets'".
With more than 60 per cent of online web visitors now reckoned to be failing to complete online order forms, there is clearly potential for this sort of service. And RealCall claims that while others may want a piece of the action, doing so will be difficult. Not only is RealCall convinced it has protected its intellectual property, it says that behind the simple idea is a "great deal of back-office infrastructure". Getting to this point has clearly taken a good deal of effort, as well as cash. While the bright idea originated with himself and co-founder Martyn Walker, Mr van der Kleij is quick to point to others' roles.
In particular, RealCall is notable for being one of the highest-flying examples of what is becoming known as the "Silicon Beach" phenomenon.
While RealCall now has an office in west London, it is still based on the south coast, where Sussex Enterprise is helping the area around Brighton to shake off its reputation as a somewhat decaying home for pensioners in favour of an image as a thriving centre for entrepreneurial talent.
Tony Sheehan, executive director of Wired Sussex - which began as an independent group formed by local authorities and business people before joining the larger enterprise body earlier this year - says that with about 350 registered companies operating in multimedia and related fields, the area has one of the world's most significant industrial "clusters".
RealCall is one of three or four that so far have developed a global presence, but Mr Sheehan is confident many others will follow.
Just as with the rather better- known biotech and hi-tech cluster around Cambridge, Brighton offers a pool of talent - partly filled by the local university - and the networking opportunities that develop when similar businesses are drawn together.
RealCall puts such a value on the help the community has given that it recently sponsored an event at Gatwick airport that gave firms like itself the chance to meet would-be investors. His most important advice to start-ups looking for venture capital? Start your presentation with the words "We make money by ..."