RTL-SDR units, $\textrm{dBm}$ I am using the Python rtlsdr library to get complex samples from my RTL-SDR USB stick.  I am getting power by squaring the real and imaginary components of these values, and adding them.  


What unit is the result in?  
If not $\textrm{dBm}$, how can I get to $\textrm{dBm}$?
It's very hard to associate the numbers you're calculating with the actual signal power at the antenna. The SDR will filter, amplify, and AGC the signal, and then it'll convert it to digital. At best, you can say that the power you're calculating is somewhat related to the true signal's power.

The power you're calculating is in linear, not logarithmic, scale. To convert to decibels, use the usual formula. However, be aware that the reference inherent when using decibels is not well specified in this case.