Hairball alert. This has been bugging me recently; I've concluded there are three devices I want.

The first device functions as a phone above all else. I also want it to be a decent MP3 player - at least 4GB. It must do calendar and contacts well. Email is good. I don't mind if it has a camera too and maybe some games but it's not critical. However, it's very critical that it has a really long battery life. It makes sense that it would be a flash-based device and must survive nasty shocks. The good news is that these devices are coming along and they're getting better all the time. I'm looking forward to see how the iPhone challenges the market.

The second device is essentially a PDA with a replaceable laptop hard disk. I want it mostly for portable media storage - pictures, music, video, PDFs. It needs to playback on either a small screen or external TV's. I'd like A2DP support. I want to plug it into the car as my main music source. It must hold my entire music collection. I want it for backing up digital photo's on CF and SD cards while I'm travelling. I want it to be a USB Host so I can manage the files on my phone/music player and external USB hard disks. I would like a few simple PDA-style applications - GPS navigation and Internet browsing would be my top picks. Some games would be cool too. Long battery life would be great but isn't as critical as my phone since I expect to carry it less and plug it in more frequently.

I can't find this second device - yet. The closest beast is the Epson P-5000 but it's very expensive and the hard disk can't be replaced.  While I really like the media playback angle, the killer application for me at the moment is CF/SD photo backup and storage. To that end, the Hyperdrive Space looks like a good deal. Nextodi have some interesting products too. Archos does good stuff but they don't do backup.  I think there's a real gap in the market that ripe to be filled. The trick is to keep it very small with massive storage and focus on a few key scenario's and not be too general.

The third device is a laptop - a full computer with a keyboard that can run any app and is comfortable to type on.

These three devices would work well together. The phone+player lives in my pocket and goes everywhere. Its job is communications, time organisation and a bit of entertainment during commutes. The PDA+hard disk is my travel device and lives in my shoulder bag. It has all my entertainment and backs up my digital camera. I want maps and guidebooks on it. GPS navigation and Wifi Internet access would top it off. The laptop is for applications. It can use the PDA+hard disk as an external storage device. Meanwhile the PDA+hard disk can change the photo's and music on the phone.

I'm watching the Ultra Mobile PC products as the niche they fill is intriguing. They combine the laptop function with the portable media storage function. However a generic pc has to have a decent sized display screen for the UI to work so they can never very small. That's why I believe the PDA format is better than a UMPC. However the PDA will be relegated to a niche scenarios if it doesn't get more storage. For travelling, I'd love to have this PDA + hard disk device but I can't find it yet.