We have a customer with some water and electricity meters that cannot be added to the fixed network at the moment, but we'd like to manually read these and include the data in the monthly billing run. Can we do this using a Nokia cellphone, running the CaptureTotal app? Would we set these meters up on PnP as 'Virtual' meters?

Yes, you can add the meters as virtual meters and then use CaptureTotals to enter the totals manually.
CaptureTotals will only capture one total every time you go to site.
If it is an Elster, I think it might be easier (and have better data) to download the meter using PMU, export the readings as csv
and then upload the readings using Tools->Import Readings.

O, you can also use your laptop as a modem/etherpad.
If you have a 3G dongle for your laptop, you can take your laptop to site,
hook up to the meter with an optical probe and then run a small application that will connect the meter to pnpscada.
You can read about it in this thread:
http://wiki.pnpscada.com/showthread.php?309

If these are manual meters, then, yes, the preferred way to add them would be as Virtual Meters, with no dependent meter/s specified.
Yes, you could use the cell phone app to capture the totals, or there are various screens available to also type in the totals on a web page. You could capture it one at a time in Edit->Meter Totals, or you could capture them in bulk using Tools->BulkCaptureManualReadings. If you have MD to capture (kVA); you can use BulkCaptureManualElectricityReadings. Another bulk capture screen that some client prefer is Edit->Manual Entries. This one works well with a setup like with the cell phone app, because you can choose between roles, to see the meters to capture readings for, based on the relevant meter reader role.

Note, we're still asking one channel for this, even though it is manual. We don't really want to promote manual meter reading, so that is why we ask the same for simple automatic meters and manual meters.
Actually, the channels is dependent on what gets put into the DB.

Thanks for the info. This would be just a simple kL or kWh total for the manual meter - so I guess just 1 channel per meter on PnP.