predict the computerised movements of shares and markets using home-made software.
Despite battling serious ill-health, 56-year-old Mr Strang has, since 2012, turned his Trends & Targets website into a market-watchers' cult.
Thousands of investors follow the nightly guidance from deepest Argyll, which tracks the daily gyrations of individual shares, commodities and stock market indices, and sets parameters for their rising and falling - with surprisingly accurate results.
He doesn't tip shares and he doesn't trade them. "I look at the way prices have been moved and that essentially gives me the parameters that the market is working to," Mr Strang explains. Prices are moved not by market-makers, as investors might imagine, but by software, he says. "We would all like to agree that the stock market should be the representation of free market forces, but if I get things right to the penny it means the computers are in control - I am mapping computers, not free market forces."
His followers have been attracted through investor publications and a tie-up with Interactive Investor which the software inventor says has proved successful but not yet lucrative.
Mr Strang is the son of a Glasgow motor business owner (Peat Road Motors) who turned his attention to inventing. He won a John Logie Baird award in 1991 for devising the original 'clip-phone' for mobiles. He recalls: "Motorola took an option on it, but I couldn't afford the international patent renewal bill of £42,000 so it lapsed. Then the first Bluetooth used part of my design."
That followed an earlier coup. "I sold a system to the Scottish Office for £3000 in 1986-87. They said 'do you want to rethink, you are displacing five systems costing £150,000 a year each?'. I said it only took me a month. It was introduced at government centres and I believe Margaret Thatcher sent her first email using my system."
He thought he had finally hit the jackpot when filling station software he had designed for his own business, to measure how much petrol was in the underground tanks, was adopted by Texaco/Chevron. "I spent a year developing software for them, it was all accepted, everyone was happy and I was going to be super-rich. Then their accountants said they could do it better - but it did allow me to clear off my mortgage."
Mr Strang sold his filling stations but still owned an off-licence and a computer shop which he ran until a stroke forced him to think about retiring, and in 2007 he had cash to invest as he planned his move out of Glasgow to Argyll. He says: "Everyone told me the safest place to put all my money was in the stock market - with 20/20 hindsight it was probably the worst advice I have ever been given."
The crash wiped out his shares, notably the 250,000 shares he had acquired in RBS, and still holds. But it prompted an ingenious response, from a man who knew nothing about shares or markets. "Since that point, I have been finding out how to get my own back."
Mr Strang set about devising software that would analyse the historic movements of any chosen stock, index or market and predict their future trends in either direction, setting primary and secondary targets up and down at any given time. In 2010, he set a bearish drop target for BP which, when the Deepwater Horizon crisis broke, was met to within 5p.
Heads began to turn when in a blog for a respected investment website in June 2012, Mr Strang said that Lloyds, once it broke through a certain threshold, was set to double. Followers were rewarded, and they began to flock to Trends & Targets, among them what Mr Strang calls "some serious investors". Given the lack of track record on Royal Mail, he was pleased to have predicted its first day's closing price last October. "I could see how the share price was being manipulated by the trading software and I was right to the penny." In December, he predicted that once insurer RSA started falling it would bottom at 78.2p. "It fell to 78.5p. It needed an event to take the price down to the target. If something has met our criteria it is going to go to target. The one thing I can't give is a time-frame, I don't think anyone can."
He admits to "an instance where I got something completely wrong", only because he says it has been so rare.
Undaunted by a March 2012 diagnosis of leukaemia and gruelling chemotherapy, Mr Strang, with help from his daughter Jacqueline, has built Trends& Targets into a near-unique service. "Until a month ago, I didn't know of a single company in the world doing what I do, but it transpires there is a very large company listed on the Toronto stock exchange doing it."
Interactive Investor sends his daily bulletin out to several thousand investors, which is gratifying, but the author says: "It is supposed to generate clients, it doesn't really because people want everything free." But he hopes 2014 will bring a deal for a premium subscription service.