Yes, 9@9j really is the name of Philips' upcoming mobile phone. It'll be fun going into Carphone Warehouse asking for that... But the candybar handset does have one innovation - there's a slot for a AAA battery in the bottom.
The technology comes from Israeli firm Techtium, and it's called Backupower. The 9@9j is the first phone to have it inside. Battery firm Energizer is involved too - I grabbed Moti Puran - its Manager OEM Europe - to explain it.
"It has a standard lithium ion rechargeable battery, but it has the option to put a AAA battery in, and it'll give you three hours extra talktime," he says. "If your lithium ion battery goes dead, the backup battery kicks in, and starts to charge the lithium ion battery, so you can start using the phone straight away."
The 9@9j goes on sale in April. But hey, it isn't just Philips doing this kind of thing. Nokia will soon be launching an external charger using the same technology, so you'll connect it to your phone to have the same effect. It's called the Nokia Extra Power DC-8, and will use AA batteries. Look:
This has been the one and only post about batteries that I've filed from Mobile World Congress. Resident battery correspondent Gary will be proud. Maybe.
Find more mobile news in our Mobile World Congress 2008 category