A 4G modem would probably be overkill, but one might be able to do it for free with lorawan. Or alternatively a big label saying "this bike is GPS tracked" with absolutely no extra hardware at all and hope that bike thieves are dumb fucks.
NY:
https://nyc.streetsblog.org/2024/09/12/the-river-wild-bikes-...
Michigan:
https://www.mlive.com/environment/2024/08/seriously-waterway...
DC:
https://irrigationleadermagazine.com/not-so-convenient-why-s...
Ohio:
https://www.nbc4i.com/news/local-news/columbus/30-electronic...
My bike, on the other hand? A thief could just find and remove the tracker - or strip the bike for parts.
But yes I do partially agree that it probably wouldn't help much, since it's more about the thieves not wanting to mess with a company with funding and a legal department behind it vs. some random bloke who they can rob with impunity. Private bike security firms might be an answer to the issue, you pay a monthly subscription, they put their own trackers on your bike, employ licensed people who retrieve stolen ones at gunpoint and guarantee protection up to some total cost. Probably not cost effective though I guess, given that the police themselves have given up.
I think you can learn a lot by looking at how bikes -- acoustic and electric -- are already being parked and locked in your district. For instance my daughter is attending grad school in a big city, and while we were walking around, I noticed that the most decrepit old bikes were secured with giant U-locks plus chains. Hmmm. So my daughter rides a bike of similar ilk, and secures it in a similar fashion.
And I noticed the most beastly of chains and locks in New York City.
Plus, people generally seem to prefer e-bikes where they can take the battery pack with them.
I always lock and secure my road bike against street furniture, though.
I use normal D locks but are tempted to get an angle grinder resistant one although they are expensive - £150+.
Buy the best lock you can afford - it should be a grinder resistant one such as hiplok or litelok.
Note that while the lock may be resistant, the thing it's locked to may be easier to cut if the thief gets frustrated and has time to steal it.
Nothing will stop someone who has the time and batteries/discs from stealing your bike.
I bought one for my expensive gravel and have been happy with it so far.
From the safety point of view it's not as bad as it seems on the first glance, especially if you don't plan riding on it faster than 20-30 km/h.
Legs. I have legs. They are built in. I can just use them. I can always bring my legs onto the subway.
If they don't go fast enough, then I have two options:
1. Give myself more time.
2. Jog or run. This will make me sweaty. Maybe I will want to shower at the office. That's an option. It will make me healthier, if I do it.
There is also a third choice:
3. Obtain real estate in such a way that substantial travel is not required.
Clearly most people will look at these options and say, "FooBar, you are insane."
It's simultaneously the easiest solution to the problem, and the most difficult.