I don't know if they give off anything. We've been using temperature detection charms and they're spotty at best, so it might not be the way to go.
No idea how long it'll last. The train does tend to keep the lethal things shorter than most events. We had killer wasps for a while, and that only went for a week. The rest of the time in that scenery was blissfully quiet.
I don't know how well the hacking will work. The train resets things every night. Its own things, I mean. If you break a window, it's fixed the next morning. Crunch your phone, it's fixed the next morning. I know people have tried to hack things, and I don't think it ever went well. Or for long. But hey, maybe the train's breaking down again and it'll cave for a little while.