EastHarlem_E, this comes up a lot, and you're right to be suspicious. If you're rent stabilized, the landlord cannot add a new security deposit or access fee in the middle of your lease just because they decided to modernize the lock. The key word is new. A key fob deposit is still a security deposit for legal purposes, and a tenant in a stabilized unit generally doesn't have to start paying a fresh deposit for something that replaces a functioning key. They also can't condition your access on signing a rider unless the work is required by law or your existing lease actually gives them the right.
First step: read your current lease and any riders. Look for language about building-wide security systems, locks, or charges for keys. Most standard stabilized leases won't include a fob-deposit clause. If it's not there, they can ask, but they can't make you. Second: send an email or certified letter saying you do not consent to the new deposit and you'll continue to require a working key to your apartment at no extra charge. Keep it polite but in writing.
Practically, even if you accept the fob, insist that the deposit be treated as security: it should go into a separate account, be refundable with interest where applicable, and there should be a receipt. If the old deadbolt is still on the door and you have a key, they may have done this for common areas only; that's less serious. But if they've removed the key cylinder and the fob is now the only way in, that's an alteration of access, not just a bonus.
If they push back, file a complaint with DHCR or call 311 and ask for a tenant helpline referral. In my old building on 90th, the landlord tried exactly this after a lobby intercom upgrade. A couple of us sent letters citing the lease, and management dropped the deposit for stabilized tenants. They still rolled out the fobs for the main door, but nobody had to pay a new fee. Market-rate tenants had less leverage, so your status matters.
One caveat: if you lose a fob, the replacement charge has to be reasonable and based on their actual cost, not some made-up number. Don't sign a rider that says 'lost fob fee' without a cap.