messaging from laptop to cell phone
https :// computer . howstuffworks . com/e-mail-messaging/sms.htm
Only gave this a glance (but be better), seems like a fairly simplified scheme compared to landlines of old: sender transmits a message via certain protocol, sms center receives it, waits until the target phone is in range, then relays the message to it.
Any device, putting forth the effort & credentials to achieve it, can conform to a protocol. The center's willingness to forward the message requires effort and incentive as such, namely financial.
If you're in the USA, sure, a quick search yields several bulk messaging services. Elsewhere, companies will most like have such capabilities by now, but whether it's open to individuals cannot be guaranteed.