Does the world need another portable battery meant to charge your devices in a pinch? Probably not.

But I dig the minimalism of this one. Instead of requiring you to carry around yet another thing, it turns your existing iPhone wall charger into a backup battery.

One less thing to forget when you’re packing up the hotel room!

Just announced this morning by the same folks who built the itty-bitty ChargeKey iPhone cable, the NomadPlus is a 1,500mAh battery that slips right on top of your iPhone wall wart.

(For the curious: once you account for output efficiency and whatnot, a 1,500mAh battery is big enough to charge a dead iPhone 5S up to about 70%. Also worth noting: the output is capped at 5V/1A — perfect for iPhone, but it’ll make charging an iPad super slow)

The pre-order price is set at $40 — but according to this Instagram post from the company, the promo code “nomadplus” will drop that down to $20. I just gave the code a shot and it worked, though there’s no word on how long that’ll be the case.