The cheapest temperature sensor with GSM module for remote monitoring?

Hello
I need the cheapest solution to measure the temperature in a building and send it remotely a few km away.
I was thinking about a sensor with a built-in gsm module which would send the measurement result e.g. every hour? Is there such a thing in normal price?
So far I have only found such a thing as a component of alarm panels for a few hundred dollars... overkill for me...
I only need it to measure the temperature in an unfinished building to know when it drops below zero (there are water pipes inside and I have to go and turn on the electric heater). Ideally I'd still like to have some sort of module on site with a relay output to turn on the radiator.
Budget up to £150?
Alternatively, maybe there are some temperature sensors that can be connected to a mobile phone which I would leave on site e.g. via microusb or BT ? Surely there are some android apps that would be suitable for this?

Hello

tomjey wrote:

I need the cheapest solution to measure the temperature in a building and remotely transmit it a few km away

tomjey wrote:

I have to drive to turn on the electric heater

Rather than buying expensive long-distance measuring and transmission equipment, it is better to buy a suitable thermostat which, when the temperature drops, activates the heater. When the temperature rises to a safe value for the water pipes, the heater will switch off. There is no need to wait for a message and the commute is dropped.
Regards

I have a radiator with a thermostat but so what if it has a range from 13 degrees upwards :/

You need to buy an external thermostat to which you connect the heater. If you have a knack for electronics then a simple ds18b21 application will do. There are also ready-made kits or at auctions see.

tomjey wrote:

Hello
I need the cheapest solution to measure the temperature in a building and remotely send it a few km away.
I was thinking of a sensor with a built-in gsm module that would send the measurement result for example every hour? Is there such a thing in normal price?
So far I have only found such a thing as a component of alarm panels for a few hundred dollars... overkill for me...
I only need it to measure the temperature in an unfinished building to know when it drops below zero (there are water pipes inside and I have to go and turn on the electric heater). Ideally I'd still like to have some sort of module on site with a relay output to turn on the radiator.
Budget up to £150?
Alternatively, maybe there are some temperature sensors that can be connected to the mobile I would leave on site e.g. via microusb or BT ? There are probably some android apps that would be suitable for this?

I will say frankly that the budget you have allocated is quite limited and it will be hard to find something.... As for your last question - there is an app for android (e-thermostat) that controls the heating via WST controllers, you can protect yourself from temperature drops, adjust the hysteresis, basically you set everything "your way". In my opinion, this is the most convenient solution in your case, but you have to prepare yourself for the expense of about 500 pln (e.g. warmtec regulator).
And if your budget is intact, maybe it is worth thinking about the traditional old blower, only with a wider range of temperature control?

tomjey wrote:

I have a radiator with a thermostat but so what if it has a range from 13 degrees upwards :/

Virtually any thermostat can be tuned by a few degrees, electronic ones have a potentiometer and bimetallic, direct bellows, bellows with capillary have an adjustment screw.
Just a little courage and everything or almost everything can be done, you just have to remember that the safe limit is about 5 degrees above 0. One more thing, can this heater cope if it switches on at such a low temperature?

It can do this because the room is 2m2. On the lowest radiator stage (15% power) in the -15 frost there was +10C in the room.