I wish to use a mobile phone to switch on things, I have searched this forum and read that I need a GSM modem. Is this correct? Can anyone offer any suggestions as to which ones I should buy?
No it doesn't matter. You can use a mobile, you can also use a Landline telephone. GSM modem can handle voice/data/fax. It depends on you, for what purpose you want to use GSM modem.
I wish to send a text to a device which then can do things such as turn things on/off etc. I do not whant to have a complete mobile phone attached to the side of anything I build. Is there any GSM device you can recommend?
I do not want to use the landline phone as I want to build a device which is standalone.