Clueless newbie

Hi there, I have a severely hearing impaired wife (33% hearing ability with aids) and a 6yo son with epilepsy, we use a baby monitor through the night ( kiddome) to check for seizures but the sound is so quiet through the monitors tiny speaker it makes it very hard to hear the sounds of an oncoming seizure or cry for help from his twin sister who shares a room with him. I was wondering if it is possible to wire up an external speaker maybe with battery power to get a louder volume and also maybe rig up some kind of pillow vibrator to alert us when sleeping as once she removes her hearing aids the wife can hear nothing. Any help would be greatly appreciated as I don't know how to measure the internal speakers output or wire in a phono jack for the new speaker and vibratory. Many thanks peeps.