monitors & heart rate

My son is 22 has Temporal Lobe Seizures while he sleeps.  Bad, often, wakes up covered in blood from biting tongue, and sore from the muscles.  He takes 650 mg Dilantin each day -still has them. Doctor is concerned since so many & frequent when he sleeps. Afraid he may not wake up since no one knows how long they are or last.  Advised us to get a monitor.  Can anyone recommend a monitor?  What about a heart monitor to wear on wrist?  Does your heart rate go up when you have a seizure?  We have to listen to him while he sleeps to make sure he comes out of it.  Doctor told us 1st time  may die from this.  Can anyone recommend a monitor and if your heart rate goes up when you have a seizure?  I saw those heart rate watches, with alarms.  I need something to go off and tell us he is having a seizure.   Help please.