A host of clubs are weighing up a move for former Coventry City captain Carl Baker, Sky Sports understands.
Sky Sports understands Bristol Rovers striker Ryan Brunt is a target for a number of clubs on loan.
The 27-year-old, who made seven appearances for the Hornets between 2010 and 2012, will provide competition for fellow keepers Heurelho Gomes and Jonathan Bond at Vicarage Road.
Gilmartin initially joined Watford from Walsall and has also had spells with Yeovil, Crawley and Plymouth.
He has spent the last year at Irish club St Patrick's Athletic.