In recent years I have seen an increase in parents recording (audio and video) their children/the other parent, whilst in litigation about the arrangements for the children. 

Applications about where the children will live and how much time they will spend with both parent are often the most emotionally difficult for clients.  During this stressful time many parents feel the need to gather evidence against the other parent, or evidence that they believe supports their proposals for the children.  Historically this has involved statements with photographs of the children enjoying time with the parent, and copy school reports showing how well the child is doing (or not) with the arrangements in place.  In some cases experts are reported to advise on the child's welfare and wishes and feelings.

Modern technology and in particularly the use of smart phones, has made audio and video recording of children (often without their knowledge) possible, as well as recording handovers and altercations between parents. 

In my experience the courts can frown on the collation of this kind of evidence and can view such actions as potentially harmful to the children. There are normally better ways to obtain evidence if there are concerns about the child or the other parent.