I suppose you could stick one on the inside and one on the outside, as paxys suggested. Then you'd have both deterrent and tamper-resistance.
As an extra bonus, if some schmuck tilts and replaces it, the deterrent will still be in force for the next guy down the line.
You put sticker #C097412 on the crate yourself, record the number, and the shipper takes it away. If things arrive damaged--and these are usually used on very expensive shipments--you can check the tilt indicator AND its number. I would bet it's much worse if indicator #D108523 arrives instead.
As an added impediment, they're often on the surface of the item but buried beneath a bunch of plastic wrap/padding/etc.
You'll often also put a variety of them inside.
It's not just rough handling, but temperature and humidity too. You can audit this sort of thing by sending occasional fake packages with precise recording instruments in them, but for usual shipments just use a variety of indicators.
You have #C097412. You remove it, and put on #D108523. You then replace the barcode and serial number underneath with #D108523.
Assuming the warehouse worker can afford all that, someone offering anti-tamper-bypass-as-a-service is going to run headfirst into the FBI, SCA, and other well-resourced government organizations with which a sane individual would never consider fucking. That does not lead to rising property values in Tokyo.
Tilting packages doesn’t seem particularly fun or lucrative. It’s not even a particularly effective form of sabotage: maybe you’ll increase the damaged-in-shipment claims by a bit, but maybe not.
If you’re already forging and breaking into wear houses, surely you could find something more enjoyable, profitable, or vicious to do than provide post-hoc cover to a rough shipper.
You are a delivery worker. You will get fired if you aren't fast enough. You will also be fired if you trigger a tilt indicator.
You're on your final warning, and replacement tilt stickers cost $3 on ebay.
A delivery worker won't be hacking e-mails - but if they know hardly anyone checks the tilt sensor serial numbers anyway...
I have no idea how much such a service would cost (perhaps your life is much more exciting than mine), but I'd imagine skilled forgers don't come cheap, as they could easily find something more profitable to do than faking tilt indicators.
At some point in transit, the package tips over (oops). You sneak in and swap the indicator for #D108523 while it’s awaiting a connection.
When it arrives, the recipient checks the crate against the invoice. She notices that the indicator numbers don’t match: the email says C097412, but the crate has D108532 on it. She won’t sign for it. She calls the vendor and says “There may be a problem with the very fragile, VERY EXPENSIVE microscope I ordered from you. Send me another one that’s demonstrably intact or get a service team out here NOW to check this one over. Legal says you’re not getting paid otherwise.”
Several other people are about to have bad days. The vendor checks their own logs and finds that the crate did indeed go out with C097412 on it. They proceed to ream out the shipping company. A lot of things might happen next, but after most of them, you get fired.
You might have gotten away with it if you could change that email, but how would you at the shipping company, have access to either parties’ email or records? And if you did have such access—-and wanted to use it for evil—-surely you could think of something more lucrative than fractionally increasing the number of possibly-damaged items received?