Mobile Phone for the Hard of Hearing.....

[#1]

Amplicomms M8000 mobile
Extra Large Buttons  too...
    Acoustics
    35dB voice volume (about 10 times louder than a standard mobile)
    90dB ringer volume (about 8 times louder than a standard mobile)
It also Vibrates !

Prince Philip's just got one, but then he is 93 years old...

http://amplicomms.com/index.php?en_powertel-m8000
http://www.hearingdirect.com/products/Amplicom-PowerTel-M8000-Loud-Mobile-Phone.html?gclid=Cj0KEQiAi...
Downloadable User Manual available

[#2]

Some additional options from a couple of other suppliers of equipment for the hard of hearing that I have used.
http://www.deafequipment.co.uk/catalogue/2570450/Mobile-Phones
http://www.actiononhearingloss.org.uk/shop/telecommunication/amplified-mobile-phones.aspx