Just to flip this around for a sec, but if these are friends, maybe it's a positive thing that they notice your first aid kit or a flashlight or whatnot because it raises their awareness and may give you an opportunity to get them interested in being more prepared. Maybe. Sure, sometimes it's annoying when people are touching your "stuff" but then again, it's just stuff. What is the point of that stuff? To help/assist people, you or someone else.

Of course, I'd hate to crash while driving because my passenger suddenly switched on the disorienting strobe feature of my super high power flashlight and can't figure out how to turn it off!

That said, I do prefer to keep those things low-profile mostly to lessen the risk of theft. Whatever people would normally carry will generally draw the least attention. Could be a messenger bag or daypack in many places, or something more formal in an area with lot's of white collar workers. I have had times when I kept car kit stuff in shopping bags in the trunk so it looks totally innocuous when your trunk is open. A cooler is another container I have used. It is extra handy because it can help moderate extreme temperature swings.