Jell-o (will make it easier if prepared beforehand if you little one is younger, but if they are older you may consider making it with them--learning processes is great!)
Afraid store bought playdough could hurt your little one and don't have time to make homemade playdough? This is a great, non-toxic alternative. Theo seemed a little confused at first.
He usually asks me, “mouth?” before he puts things in his mouth (thank goodness). It took him a few minutes to ask (after it was already squished between his fingers). When he asked I said it was ok, although he wasn't crazy about the taste/texture.
This is a great activity that won’t cause “worry” of them putting some in their mouths if you need to turn around for a second (because let's face it, we all need a second sometimes.)
Just like playdough you could add toys/manipulatives to it too! It’s differently textured and totally safe. Perfect for your little one who is in the need of a new kind of sensory activity!