McDermott joins on a one-year contract after being released by Newcastle where he came through the youth system.
The 21-year-old is the son of former Liverpool and England midfielder Terry McDermott, who himself had a spell at Gigg Lane at the start of his career.
Cameron had been offered a contract by Northampton, for whom he played six games on loan at the end of last season but the offer was withdrawn by the Cobblers after he stalled on signing.
The defender, also 21, rose through the ranks at Coventry and played 52 times for the Sky Blues before being released at the end of last season. He signs a two-year deal.
The duo join Gareth Roberts, Euan Holden and Ashley Grimes, who all joined the League Two club on Thursday.