IFTTT is not without it issues but I've found it to be very reliable and responsive, particularly with my tags.
Thinking about this a bit further, you want to be sure you have the best settings for the most responsive trigger from the tag:
- the 'Notify too cold after consecutive' and 'Notify too hot after consecutive' should both set to one reading.
- Threshold window should be set low. I have mine at 0.5 degrees. This might as well be 0 in a room thermostat type environment.
- 'Check temperature every' might need to be set lower. Max is 5 mins but if response is an issue maybe it needs to be lower
- Make sure updates are in line with the 'Check temperature every' setting. If the tag updates are only sent every 30 mins your IFTTT trigger could be delayed by up to that much.