Hope this helps!
The Gauge widget accepts a BaseType Number for Data.
Your data from the SQL procedure will come back as an InfoTable.
As Tori said, either in your wrapped service you can output the required field/column as Number or just output the whole table (infotable) and grab the specific field to bind to the Gauge widget.
Besides that you will likely need a refresh widget to pull the value periodically (although in 7.2 it can be pushed)