Hello @Melanie-and-Binnie0,
I think it's a good idea to provide one. It's proven useful many times and guests have mentioned it positively in reviews.
I got one in a trekking/outdoors shop. It has bandages and a small tube of antiseptic cream.
Like @Gerry-And-Rashid0 say, no tablets. If you host families with children I'd also check the kit and remove any sharp objects, like scissors, that it may contain. Remember to replace items when they reach their best by date.
It seems to be used often. One occasion was when a guest got a paper cut from a city map that I have in the room.
Steve.