The most useful sorting rule in any best car tech accessories guide is whether an item adds risk. A permanently plugged-in OBD-II dongle is a rarely-updated computer attached to your vehicle’s internal network; a good phone mount is not. Judge accessories by what they connect to, not by what they promise.
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The OBD-II port deserves respect
The diagnostic port under your dashboard is not a USB socket. It is an interface to the networks that carry messages between the car’s control modules, and it exists so technicians with proper equipment can read and sometimes write to those systems.
A cheap always-connected dongle plugged into that port is a small computer, frequently with wireless connectivity, often running firmware that will never be updated, permanently attached to that interface. Some also draw current continuously and can contribute to a flat battery on a car left standing.
This does not make diagnostic tools bad — a reader is one of the most useful things a car owner can have. It makes permanent residence the problem. Plug the tool in, read what you need, unplug it. If an insurance or fleet program requires a permanent device, that is a considered trade rather than an accessory purchase, and it should be treated as one.
Accessories worth owning
| Item | Why it earns its place |
|---|---|
| Tire inflator | Correct pressure improves range, wear and safety; most cars carry no spare |
| Jump pack | Self-rescue without a second car; the 12-volt battery fails on electric cars too |
| Quality phone mount | Keeps navigation in your sightline and the phone out of your hand |
| USB-C Power Delivery charger | Actually charges a modern phone at speed while navigating |
| Wireless projection adapter | Removes the daily cable ritual on cars with wired-only support |
| Occasional-use OBD reader | Turns a warning light into information before a workshop visit |
| Dashcam | The one accessory that pays for itself in a single disputed incident |
The inflator is the underrated entry. Navigation runs on a phone, entertainment runs on a phone, but nothing in the cabin fixes a soft tire — and on an electric car, under-inflation costs range directly.
Charging and power, done properly
Car USB ports built into older vehicles frequently deliver very little current — enough to slow a phone’s discharge while navigating, not enough to charge it. A proper USB-C Power Delivery adapter in the 12-volt socket fixes this for a small sum.
Buy from a manufacturer that publishes specifications and safety certifications. Poorly made power adapters are the accessory category with genuine fire risk, they live in a hot enclosed space, and the saving over a reputable unit is a few dollars. This is the clearest place in any best car tech accessories guide where paying more is straightforwardly correct.
Use cables with documented power ratings too — a charger that negotiates a high-power profile through an unrated cable is the same problem in a different component.
The risky category
- Permanent OBD dongles — a standing interface to the vehicle network, plus parasitic draw.
- Unbranded chargers and cables — heat, fire risk, and no accountability.
- Devices mounted in airbag deployment zones — a projectile in a collision.
- Anything obstructing the windshield — restricted by law in many places, and it removes sightlines.
- Screen-expanding overlays and stick-on displays — frequently distracting, occasionally illegal.
- Aftermarket “performance” modules that alter engine or battery management — warranty and safety implications.
- Seat-back and headrest mounts that are not designed to fail safely.
The common thread is that each either attaches to a safety system or interferes with one. Accessories that stay outside those boundaries — power, mounts, tools, cameras — carry very little downside.
Two upgrades for older cars
If your car predates the current generation of built-in sensing, two inexpensive additions genuinely change ownership rather than merely decorating it.
A retrofit tire-pressure monitoring system reports pressure from each wheel to a small display, turning the most common cause of blowouts and premature tire wear into something you notice before it costs you anything. A Bluetooth 12-volt battery monitor reports voltage and cranking health to your phone — and a failing 12-volt battery is the single most common reason a car will not start, including on electric cars, where it powers the systems that close the main contactors.
Both are cheap, both attach to nothing safety-critical, and both belong in a best car tech accessories guide well ahead of anything designed to live permanently in the dashboard.
Placement and safety
Two rules cover most of it. Nothing goes where an airbag deploys, which includes large areas of the dashboard and the sides of many cabins — check your manual for the marked zones. And nothing enters the driver’s forward sightline, which rules out most center-of-windshield mounts regardless of how convenient they look.
Loose objects deserve a mention too: anything on the dash or parcel shelf becomes a projectile in a collision. If an accessory does not have a secure mount, it belongs in a closed compartment while the car is moving.
The checklist
- Do not leave an OBD dongle plugged in. Use it, then remove it.
- Buy power accessories from manufacturers who publish certifications.
- Check airbag zones in your manual before mounting anything.
- Keep the windshield clear and check local obstruction rules.
- Prioritize the boring items — inflator, jump pack, mount — over novelty gadgets.
- Secure or stow everything loose before driving.
Sorted that way, a best car tech accessories guide gets short quickly. Roughly nine things are worth owning, most of them cost little, and the main skill is recognizing which products quietly attach themselves to systems that were designed on the assumption that nothing would.
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