I tried one of the electronic stethoscopes and hated it. It was fantastic in a house but on a moving rig it amplified background noise as much as it did the sounds you wanted to hear. Personally I found my $90 littman to work much better for ems use. An ER doc made a comment when I had it that they are only going to benefit cardiologists and any extra clarity is wasted in emergency medicine.
While you can't trust the needle bumps for a bp, they give you a ball park to pay attention to. If on your first try to heard nothing but saw bumps at about 140, then listen really close to 130-150. But as long as you are getting good on scene vitals your shouldn't need this.
My BLS squad does not carry monitors but we have a rig mounted auto BP / spo2. I hate it.