an ultra compact emonTx for installation inside wall plugs

Hi all, I'm new to the OpenEnergyMonitor project but it looks indeed very interesting! I'm interested in particular to current measurement sensors; something like emonTx V3 but smaller... do you know if there is something I can buy off-the-shelf?

The sensor I'm looking for is conceptually like emonTx V3 but I would like to have it much much smaller (say 4 x 4 cm) so that I can install it directly inside the wall plug... for that reason, a couple of "clips" (or other kind of sensors, like Hall sensors) would be enough.

I found some commercial stuff like:

but nothing so compact that it can be installed inside the wall plug... indeed, since I like small DIY projects, I'm also considering the idea of building my own small circuit. I'm considering to use a sensor like:   coupled with a small RFµ-328 and one or two coin cell batteries.
However, before embarking on such a project, I would like to make sure that there's nothing cheap off-the-shelf available :-)

So: do you know anything like what I described (very compact absorbed energy monitor for installation inside wall plugs) ?

Thank you very much!