A pager is called "busca personas" in Spanish, though most people call it just "busca".
But I wouldn't advice renting one.
I'm not sure about this but I think the pager network was operated by Telefónica only and it remains the same.
Also, you would rent the pager and pay a fixed amount of money every month. You had to send the message by calling to a call centre and talk with an operator. It was a toll free number.
The system now is different. I think you have to buy the pager and then send the messages through the call center. The problem is that they have changed the phone number and it's not a free number anymore. Now you have to dial a 902 number which is quite expensive (more than a local call).
With so many cell phones, very few people use a pager now. You can send short text messages to a cell phone for free from many Spanish websites or from another cell phone. The latter cost about 25 pesetas / message, but it's still cheaper than calling a 902 number and tell your message to the operator.
In my opinion, it'd be better if you could rent / buy a cell phone.
Regards,
Antonio
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