I don't have an alarm, but I keep my HD gun in a holster on the night stand next to my bed. A flashlight is nearby as well. I used to keep it just on the night stand, but decided that in the dark, it is better off in a holster, since I have an extra one.
I wake up instantly fully alert so grogginess isn't a problem.
I've only had a couple of instances of bumps in the night. One was unexplained and the other was a mop leaning against the sink that somehow fell over. A lot of heavy farm machinery and an occassional truck use the road in front of my house. Vibrations from that probably knocked it down.
When the last one happened, I listened at the bedroom door for a minute or so, and didn't hear anything. No kids anymore, so they were not a factor.
Not hearing anything, I proceeded to check out the noise source and found the mop on the floor.
The one time I had a real problem, it was outside and I heard nothing. Woke up to find some vandalism.