we are looking to hire a software development company to design and implement a web application to allow our customers to remotely monitor the devices we produce. If you have successfully used a company that you feel you can recommend, I will appreciate it if you can share their details.
Have you considered platforms like @Ubidots or Blynk?
This is usually the part I struggle with as well, but between these two platforms I usually find a suitable solution. There are several others well, these are good balance between cost and functionality.
+1 for Ubidots. IT is much quicker and cheaper to consume a platform than to build one. Over time, as your business matures, you may go the custom development route but, by then, you will know exactly what you need.