You do NOT need an internet connection during scoring of a game.
You do need an internet connection to download the game prior to scoring the game.
You do need an internet connection for sending data to the Sport Ngin site.
So if you game location does not have a good internet signal, download your game prior to scoring from a place where you do have a good internet signal. Then score the game. Then return to a location with a good internet signal to send the data to the Sport Ngin web site.
Note: If you have an iPhone or a cellular capable iPad then the same guidelines apply for a good cell signal. In most cases you can probably access a cell signal from a court during a game but there are definitely courts with poor cell signal coverage so in those cases you would use the same guidelines.