A Kiwi has invented a fertility gadget promising pregnancy in a year - or your money back.

Shamus Husheer, 32, made headlines in England after launching the DuoFertility ovulation detector through a company formed with fellow graduates from Cambridge University. Another Kiwi, Rotorua-born Scott Mackie, is behind the company's US arm.

The device is a thermometer the size of a $1 coin worn under the arm. It takes 20,000 readings every 24 hours to accurately alert the wearer when ovulation raises her temperature.

On sale for £495 ($1235), complete with money-back guarantee until September 20, the device also comes with unlimited support and expert fertility advice.

Husheer is confident he will not have to repay many people taking up the special offer. A trial involving 50 couples with a history of infertility problems resulted in seven pregnancies.

Husheer said the device was going through quality standards so it could be sold in New Zealand, hopefully later this year.

The Herald on Sunday understands some Kiwis have the device, sourced through friends living in England.

Husheer left New Zealand in 2002 to study for a PhD in nuclear and structural chemistry at Cambridge. He credits his success to his education at Taradale High, Hawke's Bay Polytechnic, Waikato and Otago universities and the Government's Bright Future scholarship scheme for getting him to Cambridge University.

Husheer was inspired by his mother Juliana who had to follow temperature charts to conceive him.

Data from his device could be loaded on to a computer so couples could analyse monthly cycles and plan ahead, and customers have requested a texting system to alert them to optimum baby-making times.

New Zealand Fertility Associates' clinical director, Dr Richard Fisher said Husheer's device was a "fantastic piece of technology" and helpful to those with irregular cycles.