I've got to get my own Kill-a-watt. Any suggestions on the right model? And any chance they have a connected version I could monitor via wi-fi or BT?
I'm not aware of a connected (wifi or BT) version. If you find one, please let us know.
That said, I have a P4400 and a P4460 (the "EZ").
The 4460 allows you to set a cost per KWh and has persistent storage, so if you lose power, it doesn't reset. It also has a reset button so that you CAN reset it. It's set up to allow you to easily estimate monthly (or weekly, daily, yearly, IIRC) cost of a device plugged into it.
The 4400 does not allow you to set up a cost per KWh, is reset by unplugging it (or interrupting power in some other way), and does not do any computations. Not even KWh consumed per mo/yr/dy/week, as I thought it could. It will keep track of KWh consumed, or course, so you can do the math yourself.
I bought the 4460 first ($27), then bought the 4400 later ($17) because I thought the only differences were the persistent storage and the ability to enter $/KWh. Had I known it also couldn't calculate KWh per (month, day, year, etc), I would have bought another 4460. That said, depending on what you want, the 4400 may be perfect. It's just less useful for estimating consumption over long periods if you don't keep track of when it was last reset.
OH! And something that surprised me (true of both units) is that when you plug one in, it only uses one socket, but blocks access to the other as well (in a 'normal' style US outlet). Doesn't matter which (top or bottom) outlet you use. Worse than a wall-wart in that regard.Probably more info than you needed or wanted, but since I just went down that path myself, I figured I'd share.
Oh, and btw, thanks to these two devices I know that I use about 9Kwh/day (at the meter) to do my 50 mile round trip commute, or about $20/month. I also know that the mini-split AC I installed in my garage-shop will cost me about $15/mo to leave running all the time with the thermostat set at 80F. (That's the diff between the two units! I know my AC usage in $/month, but my motorcycle usage in KWh/charge up. How do you want to think about it? The 4460 make it easy to do it either way.)