Waffles is an indoor cat but she still wears a collar and this is mainly for the bell attached so that I know where the little scamp is. Our flat is rather large and she was so small when we got her I was afraid of standing on her (which unfortunately actually happened to someone I know and the poor kitten was crushed to death).
I have the collar that Saikou recommended (a lovely pink glittery one) and it releases really easily.
However, when I first got her it kept flapping over her mouth and I was scared she would suffocate but now she is older it doesn't do that.