Apparently some manufacturers are criticising Apple for the 'excessive' security required in order to gain HomeKit certification. Some of them and some pundits may be thinking this is another fiendish scheme by Apple to achieve lock-in to yet another Apple only eco-system.
They are wrong.
Apple have shown themselves to be very much concerned about security and gone to great lengths for example to provide excellent security for iOS devices including end-to-end encryption in iMessage - so much so that the FBI is pretty unhappy.
Funnily enough on the topic of the FBI, some of you may have seen a new TV series called CSI: Cyber which about a cybercrime fighting division in the FBI, the first episode in the series was about a baby monitor being hacked over the Internet. This is actually based on true events, baby monitors have and are being hacked over the Internet. See http://www.bbc.co.uk/news/technology-34138480
So Apple is being well ahead of the field in building in extremely robust security in to HomeKit ready for when the 'Internet of Things' really takes off, it is after all far easier to do this at the beginning rather than trying to figure out how to fix things afterwards.