something like this works for me (as c code, not via AT commands):
GET yourrequesttothingspeak HTTP/1.0\r\n\r\n
or
GET yourrequesttothingspeak HTTP/1.1\r\nHost: thingspeak.com:80\r\nUser-Agent: ESP8266\r\nConnection: close\r\n\r\n
SDM Energy Meter: https://github.com/reaper7/SDM_Energy_Meter
MLEDScroll (TM1640 led matrix): https://github.com/reaper7/MLEDScroll