I wouldn't bother with X10 receivers and SDKs for a project like you describe. You're almost certain to find them too limited and lacking in documentation and transparency. And, it's easier to incorporate an adequate antenna - range of +300' is relatively easy to accomplish when you have full access to the hardware.
It's quite simple to capture the RF signals using any of a multitude of superregenerative RF receivers like those listed at...
Use a 315MHz receiver and tune it to the 310MHz that X10 uses in N. America...
or use a 433.92MHz receiver in Europe and most other regions.
And/or you can use sensors from companies other than X10 - you just need to know their RF frequency - you can usually capture/decode their protocols without much difficulty.
You can decode the signals using a PIC, Atmel AVR, or other microcontroller. Or, if you don't want to deal with the hardware at that low level, use something like an Arduino or Raspberry PI.
You can find the X10 RF protocols at...
There are other articles on my web page that fill in the details and I'll try to answer any questions. See the main web page for my email address.