I am currently looking at the EM1 system, as well as the HWg-STE. For both, do they come with a calibration certificate to validate they operate within tested ranges? Also, how often does that need to be renewed / cost? For EM1, is it email / web e

Either EM1 or STE can be provided with UKAS certificates, valid for 12 months. The sensors too would need to be certified. The cost is £55.50 for each main unit and £47.50 for each sensor. Prices exclusive of VAT.

STE cannot send SMS messages, it can though send emails and these could be converted to SMS using a third party conversion service.

EM1 has no built in managment software, you would need something like Intellipool INM to manage the device. You can add a GSM modem to the machine running Intellipool and Send SMS alerts from there. You can alert any number of recipients. You would need a standard mobile phone SIM card in the modem.