We have a potential client who wants 'realtime reads' on bulk water feeds - essentially to track flow-rate.

1. Can we do this using an RTU at the end point? We have power at the meter points, and would link the RTU to a GPRS modem for comms with PnPSCADA.
   
2. If this can be done, what is the best read interval we can get using the above setup? Is a 2 minute interval (or better) possible?
   
3. How would we set the required read interval under Edit>Advanced meter settings? I take it we'd use the Custom radio button, but how to get a 2 minute read?
   

Yes, using an RTU at the end point is good. Then you can read it as often as you want. And as long as the pulses are coming at a decent rate, you'll be able to see kl/h usage updates every 2 minutes in the Real Time Summary screen.
To see the Real Time Summary screen, you need to create a Meter Account Group that contains at least one Meter Account. (the display can potentially display multiple real time summaries: one per meter account. I think up to 12).
However, using a GPRS modem is not a good idea. I suggest using ADSL, or iBURST. GPRS is not very reliable, sorry to say. The connection will go down periodically, and then your real time value display will freeze.
The profile datalog interval with the RTU is fixed on a half hour. However, you can read the total pulse counter in real time and see it counting up, so this value you can read as often as you wish. The Real Time Summary screen reads this value about once every 2 minutes, and from that calculate the rate of change, and display that in terms of kl/h and Rands per hour. This updates every 2 minutes.
The 2 minute read on the Real Time Summary screen is a characteristic of the screen itself, it is not really something to be set on the Advanced Meter Summary screen.
Do you want to actually record profile per two minutes? Or do you want to restrict this to a real time display only? Currently pnpscada cannot log a 2 minute profile for an RTU. If we create something like that, it would be less dependable than the per-half hour datalog, because we'll have to read the RTU every 2 minutes and interpolate the profile. If we miss a read, we miss a sample. And it would require extra development on pnpscada side.
I suppose it is conceptually possible to log per 2 minutes using a SmarToo modem, where the datalog sample interval for the pulse counter is configurable. However, that would also require some development on pnpscada side. At least if you lose the connection, the profile should still be per 2 minutes, so in that sense it would be better.
So what we have right now, is support for a real time usage display in a web page on the RTU. You can also get the real time values over SNMP or OPC (if you have an OPC server on your side). You should also be able to view the real time values available in the Realtime Values screen, as a text display of the actual real time values available, at an update interval as specified by you in the web page.

Thanks Marinus. All we'd need is the 'realtime' display on a web page for now, so the current functionality is great. Logging the actual profile every half hour will be fine.