compositing while capture to laptop disk
 

I record football matches to memory chip then, some hours later in post, I composit a match clock (mm:ss) and team scores over the game footage. I then render and produce DVDs which I post to teams. Obviously this delays delivery to teams by several days.
I would like to record direct to my laptop (MacBook Pro) disk while adding the compositing in real-time. Then copy the resultant file to use memory sticks to hand to teams immediately after the match.
blackMagic ultra mini recorder looks to handle the capture side of things for me but happy to use other devices if necessary. I'm not sure what software I need to use to add the clock / score. Score is less important but clock is mandatory.

Any ideas most welcome. Thanks Ian