I have a TED-5000. Very happy with it. 15-minute install in the main panel; the bigger hassle was resetting all the clocks in the house afterwards. Connected the gateway device to my home network, now any device that has a web browser can see power usage. Easily accessible from the outside world by web browser, with the right router settings. Monitoring is down to the second, with a claimed accuracy of +/-2%
Nothing need be installed on the PC, and it doesn't rely on a PC to store data; the gateway device records the data and is the web server.
The manufacturer seems pretty open; they publish the XML format and there are plenty of people reading the device with PHP scripts and logging to SQL databases for more flexible & permanent data storage. There are a few iPhone apps and I think there is a Android app, or talk about one. You can export the data from the gateway in second, minute, hour, daily, or montly format, with the follow capacities:
~2 days of per-minute data
~66 minutes of per-second data
~58 days of per-hour data (likely longer... I've only had mine for 58 days!)
One caveat: the device that connects to the power panel (a pair of current clamps and a pair of voltage taps) communicates with the gateway via power line. Seems like many of the problems people have are related to power line communications, either due to electical noise or other power line communications devices (e.g. X-10) in the house. Some people have success with filters (extra cost), others never seem to solve these problems.
I think it meets the poster's requirements for a), b), and c). It cost me $243 Canadian delivered to my door in 3 days from a Canadian supplier
http://www.powermeterstore.com/p7774/ted_5000_home_energy_monitor.php
No connection to either company here. Just a very happy customer.