radar
seriously, nobody can come near me without me knowing when Im asleep.
I can set the sensitivity of my radar when I go to sleep.
Like, if i want to awaken when someone comes to the doorway of my room, or as far away as the front porch Im up.
And if I want to wake when my son rolls over in bed or his breathing patterns change, im up.
And on the other side...if i want to sleep through it, no problem.
I can even set my alarm, put it beside my head and decide to sleep through it and I can ( yes I have experimented with it hehe) Or I can wake a couple seconds before it goes off.
Its pretty neat once you fine tune your radar. Handy too.