Hearing Direct have some phones for those with hearing problems. They have designs ranging from Basic Candy Bar style handsets, to flip phones and smartphones.
I do not work for them; however have been a customer in the past getting phones for elderly relatives. The interface on their phones have bigger icons, the loudspeaker is also amplified and the ringer can hit a crowd-frightening 90db on their handsets.
Are you looking for something along those lines?