PeterH337/IO540,
There isn't one, and I doubt there ever will be one, the technology doesn't yet exist so we get hit with the blanket "NOT APPROVED FOR FLIGHT INTO KNOWN ICING" for almost all GA aircraft which basically leaves the pilot to decide if there is a risk of icing or not.
I spent a couple of hours in the simulator with Francis Frogbound while Verticalhold of these pages put us through a variety of icing scenarios which had been created by the training torturers. The worst case was in the middle altitudes where you would cruise a TB20, taken from FAA and CAA reports on rapid ice accretion it went from happy campers to "where the f++*! did that lot come from?" in a very short time and serious problems due to the rapid weight increase.
The day job aeroplane can even warn me of windshear, I really wish the bugger could warn of ice ahead rather than just telling me its' happening,
my playtime aeroplane only comes out when the sun is shining at this time of year and so I've never seen ice on her, but I don't think she'd do to well with it.