No cell phone is truly Granny Friendly
To the elderly all cell phones tend to be if not "user hostile" and least "user indifferent". Most of these people spent all their lives with wired phones and cell phones have completely different properties:
1. No dial tone. Once upon a time this signified your phone was broken.
2. Because there is no side tone coming out the receiver, the phone always sounds "dead" when you are talking.
3. Wired phones are full duplex, cell phones aren't. With a cell phone you can not easily interrupt an overly talkative party with an immediate comment. You have to wait for a pause, and time your response so you can break in while he takes a breath of air.