you can buid a vehical tracking system perhaps.
or leave it attached to a computer. its duty would be to send sms notification for new mails. peraphs yoy can write software to send across the whole mail as mms ?
you can buy a light switch from a electronic company as a project which can turn on any thing up to 24 volts it use a ldr to detect the light on the mobile phone it does not cost you any thing for the call as the mobile phone will not get answered hope this will help.