Keyless entry systems allow you to unlock and sometimes start a vehicle (or open a home/building door) without using a traditional metal key. They've become the standard in modern cars and are increasingly common in smart-home locks. Here's a breakdown of the main types, how they work, their pros/cons, and security considerations as of late 2025.

1. Types of Automotive Keyless Systems
Passive Entry / Passive Start (PEPS) • Walk-up unlock, push-button start • Key fob in pocket/purse • Range: 1-3m • Found on most new cars (Toyota, Ford, VW, Tesla, etc.)

Phone as a Key (digital key) • UWB or Bluetooth-based • Smartphone or smartwatch • Range: 1-30m • Tesla, BMW, Mercedes, Hyundai, Rivian, Apple Car Key, Android Digital Key

NFC Card / Key Card • Tap-to-unlock • Thin card or tag • Range: 10cm • Tesla Model 3/Y, Rivian, some Hyundai/Kia

Traditional Remote Keyless Entry (RKE) • Clicker buttons • Press buttons on fob • Range: 20-100m • Older cars, aftermarket systems

Smart Key with Rolling Codes • Mid-2000s style • Fob with lock/unlock buttons • 30-50m • Honda, older Lexus, etc.

2. How the Most Common Modern Systems Work (2023-2025 cars)
Low-Frequency (LF) antennas in the doors and trunk (125 kHz) constantly poll for a valid fob.
When the fob detects the LF signal, it wakes up and answers back via Ultra-High Frequency (UHF 433/868 MHz or Bluetooth/UWB.
Ultra-Wideband (UWB) added since ~2021 (BMW iX, Mercedes EQS, Apple Car Key, etc.) measures time-of-flight, so the car knows exactly where the phone/fob is (front, rear, inside, outside)/ makes relay attacks almost impossible.
Passive start: Once you're inside with a valid credential, a second LF coil around the start button or column verifies the fob/phone again before allowing engine start or "Ready" mode in EVs.

3. Pros vs Cons (2025 perspective)
Pros:
Huge convenience-no fumbling for keys.
Phone-as-key systems mean you never forget the fob.
UWB largely defeats classic relay attacks.
Sharing: send digital keys via messaging (BMW, Mercedes, Tesla, Android Digital Key Plus).
Walk-away auto-lock.

Cons & Remaining Risks
Battery in fob dies / most fobs have a hidden metal blade or NFC backup; phones have low-power mode.
Relay attacks still possible on non-UWB systems (common in 2015-2022 cars).
Signal blocking pouches (Faraday bags) still recommended for older cars.
Some thieves use "code grabber + jammer" combos on rolling-code systems.
Phone battery dies / many brands now support Apple/Android "Power Reserve" (works hours after phone is dead) or backup NFC cards.

4. Home / Smart-Lock Keyless Systems (for comparison)
Bluetooth + keypad (August, Schlage Encode)
Wi-Fi smart locks (most current Nest, Ring, Level, Aqara)
UWB (newer Philips, Yale, Aqara U200)
Matter/Thread support becoming standard in 2025.

5. Security Recommendations in 2025
Buy a car with UWB digital key support if theft is a concern in your area (BMW, Mercedes, Hyundai/Genesis/Kia with Digital Key 2, Volvo EX90, Polestar 3, Apple Car Key cars, etc.).
Always keep fobs in a Faraday pouch/blocker at home if you have an older non-UWB car.
Enable PIN-to-drive or sentry modes (Tesla) or similar secondary authentication.
For home locks, choose ones with UL 437 or BHMA Grade 1 physical security plus encrypted wireless.

One-sentence verdict (2025)
Cars: Get a 2022+ model with UWB/Phone-as-Key and you're basically theft-proof.
Homes: Any major-brand Matter/Thread lock (Yale, Schlage, Aqara, Level) with Apple Home Key or Google Home support is both convenient and secure.

Both car and home keyless systems are now safer and more reliable than traditional keys for everyday use.