I know it is off-topic, but why not drop the payload if the "Front" unit reaches the actual kite?
Do you have to be able to wait there indefinite or to drop it mid-line?
Anyway, the component you found and works for you is definitely a lot more expensive than a ESP8266 based system
It depends to which extend you want to optimise cost over convenience, but if you scale up, you can save a lot with further innovation. And it would open up a whole lot of other options in the process.

 

There was a suggestion that an ESP8266 be used with a smart phone. Have not been able to find the
dimensions of the ESP8266 but it seems to be much larger than the QIACHIP system. The system needs
to fit

The ESP8266 is about 3 x 15 x 25mm.

 

Look for ESP07 which is my favourite. It is 21*16mm and allows an external antenna if needed. It has a ceramic antenna built in.
There are other ESP board models all following the pattern of ESPnn. Nowadays 1-2$ a piece. Run of 3V3 so Li-Ion battery comes easy as well. But not as ready made as the model you depicted... You wil need to add the peripherals, the software etc. yourself.
Again, if you start running quantities of this product, this is the next step.