The following functionality enhancements might be done relatively quick and easy:
To achieve guaranteed notications delivery from microcontroller to server extra logic on microcontroller and/or mobile phone side might be appended. At the moment there is no validation if HTTP request to the server failed or not.
12V to 6V adapter would allow to power
the complex from a 12V car battery. Adapter's schematics and PCB
layout will be incorporated in the next UserGuide revision.
Some settings would be better to move out from program memory to EEPROM and make them configurable. Some working cells would be also better to move from RAM to EEPROM to prevent them from losing when power is down. It would be a good idea to configure them by SMS from master phone number.
TTL to RS232 hardware converter would allow
to use GSM modules such as Siemens TC35i, MC35i
etc. Converter's schematics and PCB layout will be incorporated
in the next UserGuide revision.
Bluetooth adapter capable of wired
COM port emulation and plugged in the same manner as
TTL to RS232 converter would make it possible to
interact with new types of mobile phones even if they support only
USB as a physical connection.
Additionaly it would be desirable to have the following features but it requires more efforts:
Remote firmware update feature via TCP over GPRS transport.