The National Network of Regional Safety Reps have produced a new resource for safety reps who cover numerous/remote workplaces. This new checklist is a word document consisting of 11 key questions that you could email to members of sites you can't easily access.
You could ask members to get together to review the checklist, which should assist them to think about what are the crucial health and safety issues in their particular workplace.
You will need to arrange with them who will feedback to you if there is a particular issue they require your assistance or advice on.