If I need my electronic diary while I am in the pub or at the sports center, why not just telephone that portion which remains at home. Enter the security code and access it through the phone. When I reach home, I re-marry the phone with the mother unit. The system can then control my environment as predicted by Bluetooth fans. Yes, one device to do all seems, on the surface, to be a good idea, but underneath it quickly becomes impracticable.
Battery life is today a major consideration.
Run the battery down checking the diary and suddenly you are out of communication because the phone relies on the same battery. A colleague of mine had his mobile phone velcroed to his iPaq, both communicating with each other via infrared reflected by a small disc stuck to the top of the aerial mast. SMS Text Messaging with no advertising. My son and daughter do not ask for phones that look trendy anymore, with colorful fronts and small in size, but the one with the best SMS texting system and with so many free text messages per day. An easy question to answer, the one of course that is used by the device system the public chooses as the winner.