Those cool ideas are now out of date.
My son turned me on to Boost jump start batteries:
https://www.amazon.com/Allstart-560-Boost-Max/dp/B00RZE1FB2
The link is to the one I currently use, but these things are common as dirt now.
They also have USB ports to charge your iPad and iPhone, have a flash (and flashing!) light, and come with jumper cables and a pack of connectors for various gadgets that need their batteries charged.
Prices and power levels vary from cheap to a lot, but the Allstart and the MAC Tools versions I've had have been great.
It fits in my engine compartment thru the oil inspection door, so I could start the engine, then (carefully so as not the meet the prop) reach in and remove it, then close the hatch.
I know that sounds a little risky for some, but compare that to hand propping?
Or, inside the cockpit, I could connect to the power bus stud and wait until the Ship's battery gains enough charge.
Also, if I lost alternator power in flight, I could connect the boost battery to the power bus stud and add some endurance to the next airport, to keep the radio, transponder and EFIS up and running.
Typically it's used to keep the iPad fresh during hours of Foreflight, but I should build in a Ship's USB port.
Then I carry it in the car, it will jump a big V8. It's started my old Ford tractor too.
Carry it with you, have it ready for use on anything: Airplane, Car, Motorcycle, Riding Mower, transistor radio etc, etc.