And it has been hundreds of hours in the making - all outside of class time, going through prototype after prototype and learning specialised computer software and coding, with digital technology teacher, Medwyn Popplewell for the in-built computer. The computer was supplied by Jaycar Electronics Hastings.
"We can't believe something like this is not out there," Popplewell said. "What these boys have come up with and been able to create is amazing."
Things like getting a patent for their product are now coming to the surface - something they never considered at the beginning.
However, it is not finished entirely, with final tweaks yet to be made, including to the size of the battery.
Their aim from the get-go was to make their device as affordable as possible. Similar devices currently on the market cost about $1500 each and only monitored either rainfall or floodwaters, whereas George did both for $300, Selwood said.
Fertiliser company Ravensdown has signed up as a commercial partner to help develop the product further and regional manager George Williams said there was huge potential for farming customers to use the device.
"Because farmers are all affected by weather events in every season, that's drought or rainfall, any means of indicating that is valuable.
"It is a great initiative that the school has come up with, so we are happy to support anything that will help the wider community with weather events."
Williams said there are similar products to that of George in the marketplace, but none that specifically alerted.
Hawke's Bay Civil Defence emergency management group controller Ian MacDonald said it was great to see a bit of Kiwi ingenuity and use of technology to help solve a problem like this.
"The sort of low cost warning device the St John's students developed could be an option for farmers who have smaller water courses on their land that flood – to give them a warning to keep safe or move stock and equipment.
"The only limiting factor I can see is that if you are in an area with no cellphone coverage the system would not work."
He said the device could supplement the existing HBRC 24/7 flood warning network which works along similar principles but is focused on their major river systems where there is the greatest risk to communities.
However, George was created for a bigger purpose - funds made from the device will be donated to their social enterprise partner, What Ever It Takes (WIT) and with five sold so far, they have generated enough revenue to break even. The rest will be donated to the Mental Health Foundation.
The group, which consists of Selwood, fellow CEO Kadyn Newport, Rhyva van Onselen, Ben Gardiner, Shea McDonald, Zayne Coffey, Jake McIvor and Jack Gardner, has spent several hours at the Hastings base making lunches and spending time with the people receiving care.
"It has been a humbling experience for us because people with mental-health issues in the community are marginalised and when you engage with them and understand their stories, they are not different to us," Gardiner said.
For YES, the group are coming to the end of their journey, with their annual report yet to be finished. Afterwards, they are planning to see where it takes them.
George will be at the Hawke's Bay Farmers' Market this Sunday and with the support of Ravensdown, the product will be sent to Samoa later this year.
