How to load some code from specific location from EEprom?

I'm making a plan for such a scenario:

1. Think that I developed an application, wrote it to the device, tested it, and send to the field when it's ready.
   
2. It turns out, my application had a bug.
   
3. I have a very very good idea(!) that the problem is just the var x = 1;, it should be var x = {1} (watch the typo)
   
4. I send the code to the device, and the device is bricked now and I have no option to fix the last wrong app...
   
   

My plan as a precaution is the following:

1. I can send this untested code with a mark to indicate "to be tested",
   
2. device would download and save it,
   
3. make it loaded on next reboot, and
   
4. watch for a specific "heartbeat" sign (for example, I can set a timeout for a specific FlashEEPROM location value and set the "OK" value over socket connection, which will guarantee that my second application boots and connects correctly).
   
5. If no heartbeat is found within a timeout, then old code will be loaded and new code will be discarded by the device (bootloader) itself.