Healing device

[didub]

I'm running a D&D 3.5 game, but I'm twisting the setting a lot. Basically, there's no magic except for sorcerers, which are rare, but the world is advanced to approximately the late 1800s. I want magic healing to be possible, but it should come from a device, not a deity or other higher power.
Currently I'm thinking there's gonna be some device that lets the player heal a number of hit points equal to their (heal+use magic device+d20)/2 The healing takes 2 rounds per hit point healed. Additionally, unless the the user refrains from using a device for 8 hours, each time it is used the divider increased by one, so that after one used the result would be (heal+use magic device+d20)/3

However, that's not all. I'm also going to design a prestige class that basically lets them use the device to get cleric spells. This is the part I'm stuck on. I'd like the device to have a power source that recharges daily, and a crucial part of getting higher level spells would be finding more power sources. I also think it would be cool if over time that got access to different types of cleric magic (buffing, healing, divining, etc.). Not sure yet if that would have to come from different devices or greater expertise in using the regular device.

Any input would be appreciated, especially on how these rules good be abused.

[Caldarin]

Firstly, this is basically my campaign right now too (but with clerics) the wizards got purged from the world because the mage's guild leaders wanted to become gods and the chuch didn't like that

but I like the sound of the device- wonders of modern medicine.
The rest of the cleric spells though sound interesting, but I'm not sure how it's gonna factor in to the device.

[Ashtagon]

Can a single character use multiple devices in the same hour?

Can multiple devices be used on the same character in the same hour?

Based on the rules as written so far, as characters level up, hp is going to scale up far faster than rate of healing. Is this is intentional?

[didub]

I wrote some rules that I think I like for the straight healing aspect of it, and edited them into the post above. Still working on the access to clerical spells.

Ash- You can be healed by multiple different devices fine, but if you continue to use a device, the increased divider doesn't reset with a new device. It's a result of your own fatigue.

[Ashtagon]

As written now, it is effectively full healing outside of combat.