Things like webcams etc can be controlled centrally leaving you with no options as to what's going on.
As far as as them knowing when you are doing or not doing, they probably have been able to do that for ages. They may or may not have done it, but now they are keeping the right side of the law by keeping you informed.
Presumably, email/internet usage policies are already part of your contract/work handbook, so this is just taking it further or making it legal.
If it has not been agreed with unions etc, there may be a problem.
If it is not included in your contract/work handbook then they may be in breach of the law.
Any monitoring, except for detection/proof of "illegal" actions can be deemed illegal itself as it may be a breach of privacy laws.
