HI,
can you please detail the following:
Type of sensors you plan to use, IE for GAS which GAS ? GPL ? Methane, CO2, CO ?
Moreover, with GPS tracking, what do you exactly mean ? I assume is just to get the exact time and record time to calculate the total "on" time
Also I would like to build a real prototype and send it to you, this would not add much to the cost since I've no mark-up: I expect that parts & the delivery will add to costs some 100$, however I can be precise only if you provide the above details.
Also the realization time could change: it much depends if I find the sensor and if is a "strange" one which difficulties I can have.
Alex.