AuctionRadar installs straight from this page. It opens in its own window with no browser bar, keeps working when you lose signal, and puts the feed, steals and your alerts one tap from the home screen.
Press Install above. If the button stays disabled, open your browser menu and choose Install app or Add to Home screen.
Open this page in Safari, tap the Share button, then Add to Home Screen. Safari does not allow an install button, so that is the route Apple provides.
A Play Store listing is being prepared. Installing from here gives you the same app in the meantime.