idle rainy day pondering - cheapest way to have a phone number + a little data for a backup iPhone?

[clay]

I have a now-unneeded iPhone 5s (Verizon, GSM sim unlocked). Thinking of keeping it around, both as a backup in case my main phone dies. Also considering keeping it to take on bike rides/runs as a audio listening device, fitness tracker/GPS device, and emergency call/text device. To that end, for it to be truly useful, it needs, at a minimum, a small amount of cell data. I could get a google voice number and route all calls over the cell data, or could sign up with a super cheap cell plan. I like the idea of having a device that I can take with me that doesn't ultimately matter whether it gets wet, breaks, gets lost or is stolen.

Wondering if there is a way to get data or maybe data+calls/texts for under $5/month? Free option would be a no-brainer. $1-$2/month probably still a strong "yes". But even $5/month seems like more cost than it would be worth to me.

any tips?

[clay]

maybe 50mb-200mb/month data would be sufficient

[Acer]

$5 a month is hard to come by for an LTE smart phone. BYOP Tracfone is close, $10 for automatic monthly plus tax & fees. You might get to less than $10 a month on average, if you carefully buy bulk minutes/data as needed and not automatic renewal.

[clay]

yeah, I know it's a long shot. Would be nice if I could buy maybe 1GB/year prepaid for $10-$15 total and then just use VOIP for calls/messaging as needed. If I could find something like that, I'd jump on it. Would be a perfect emergency device for me.

[Mr Downtown]

FreedomPop or Ting.

[Buzz]

We use our VOIP provider's app on decommissioned (and previously unlocked) phones via wifi only, and that works pretty well. No SIM needed, and no costs incurred until swapped back into regular cellular service. Only extra cost issue, is that some carriers' SIM's age out if not used for a period of time, and if/when recommissioning a phone there may be a new SIM/activation fee. Not sure what other service/plan you're using, but some providers have 4th or 5th lines for no add'l cost. Several years ago (pre-smartphone days) we had two free lines from Sprint that were great for guests, and trips to Disneyland, etc. I've seen freebie family-line deals recently, from Sprint, T-Mo, and some MVNO's, which may be a viable option.
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[cbelt3]

Freedompop SIM.

[RAMd®d]

I have a now-unneeded iPhone 5s (Verizon, GSM sim unlocked). Thinking of keeping it around, both as a backup in case my main phone dies.

Great idea! I did the same with my 4S and was going to do the same with my 5s, but it died. So, waiting for SE, I put the 5s SIM in the 4S, and I'm limping along until the SE ships.

When I get it, the 4S will be retired to back up duty. I don't know if Apple will put a battery in it. It may be too old.

[rz]

FreedomPop, as mentioned above. I bought a cheap android phone that I can put a large microSD card in to basically use as a music player. I got the Freedom Pop sim for free (or maybe $1)... they have deals all the time. After a free month of their premium service, you go online and change it to their free plan. You do have to be diligent because they'll "helpfully" charge your CC if they think you're getting close to going over your free allotment of data. Also, if you don't use the phone for a couple of months, they deactivate it until you call back. Probably not good if you're wanting to use it in emergencies. Best bet is to use it at least once a month to keep the service going.

[space-time]

https://www.xfinity.com/mobile/

my bill was $2.74 last month (that was entirely taxes and fees, comcast actual bill was $0.00). 100 MB of data, unlimited talk and text, Verizon network, and if I exceed 100 MB, $12/GB.