My Apple wireless mouse has been laggy recently. So after a bit of digging, I found that you can fix (or at the very least reduce) the problem by changing the channel of your wireless network. So I gave it a go - I changes my Airport settings from Automatic to 1, and the mouse seems far better as result.

I’ve only just done this, so I don’t know if this is going to be a long term change or not. Anyway, thought I’d share.

I believe wifi and bluetooth actually use the same frequency range (2.4GHz?) so there's a chance of them interfering, although the power levels differ in general. The ideal thing to do would be (if your kit can handle it) switch the wifi to use 5GHz instead.

That’s why Channel 1 is the best option - it’s less likely to interfere wilt BlueTooth. I don‘t have the 5GHz option here. My wireless kit is old, and the base station needs rebooting every day or so because it crashes. I expect it will need replacing at some point.

Use a wifi scanner app, there are lots on Android, I assume that the iPhone also has them. That will shown you which channels are best in you area. If you have an 11n capable router, switch to 5Ghz.