You are flying above a large lava lake in nether... and suddenly fuel runs out. Just forgotten to check a fuel/charge level before a takeoff. What if we can see a power meter wearing a jetpack or nano-suit? Something like a small battery icon or a gauge in a corner of screen.
If it is too hard to code HUD, maybe just print a warning messages like "Fuel low" and "Fuel critical" every 3 seconds while flying and jetpack's charge is lower than 25% and 10% respectively. I think, it'll we very helpful. ...and something like this for suit's charge levels.