Not a half bad idea. I'll take the idea under review, but so far I've got more than enough to do on tellmon.net. 

This is also under planning. It will probably start out with a limited set of triggers and grow over time.

Export (csv and Excel) is planned and will probably be available for subscribers only. 

I've been thinking about this. But I decided to only show the current usage over time and not try to calculate the accumulated total. One reason is that Tellmon does not use the backup sensor of the FooGadget meter, only the primary sensor. I can see from the message counter that quite a high number of messages get lost. Loosing reading when only showing the instance usage is no big deal. But trying to total the energy reading it would quite fast end up with a total that did not match the actual total on the real energy meter. I suspect the Telldus/Tellstick is not 100% reliable and that's why the FooGadget meter has a backup reading as well.

Tellmon now has 1709 sensors and 4298 devices connected that it receives values from. It receives about 10 values pr. second. This is handled quite well so far, but if I'm to support the backup sensor of FooGadget I need to do some more calculations and lookup the previous value and message count in order to detect a possible missing reading and then read the backup sensor. 

As I don't have a meeter myself the whole thing is a bit difficult to work with. I'll add your suggestion to the whish list, but I can't promise anything.

Good idea about the price.

Thank you for your feedback. This feature is already planned.

Best regards

Year, custom rage, zoom and pan is on the plan. As of now I delete data older than 1 month since just to keep the database size down. 

A subscription open via PayPal (price not decided) will open new features where unlimited data history is one of them.