Anki is a freely available (open source) digital flashcard programme that can be downloaded for various platforms from here: https://apps.ankiweb.net
Your desktop and mobile Anki apps can be synchronised very easily via a free Anki account: https://ankiweb.net/account/register
The XG2Anki service developed by Rainer Birkle allows the fully automated creation of Anki decks from XG match and position files.