A lot of comments were complaining about not getting the back cover off. I don't know if they were talking about the T100 model specifically, but I posted a video showing that it's very easy to do one handed..... Also, this product doesn't come with batteries, so I am assuming the other people had a model besides the basic T100 model.
The back clip seems a little chintzy, it's small and there is no articilation so I doubt it's really helpful for thick clothing. The units are small, but they feel solid. They are cheap and will work for what I need them to do.
I like that they use AAA batteries instead of an internal lithium. You can get some rechargeable eneloop batteries and this thing will probably last a LONG time. Internal lithium batteries can sometimes be a pain to replace when they go bad.
I have no complaints. I can't comment on range, for the price point though I not expecting much. These are very simple to use, which makes sense because a child should be able to operate it as that's probably the target demographic.