Unfortunately, this is not something that we support at the moment.
It is possible accessing your account on multiple devices by logging in with the exact same login details, but we are unable to guarantee that the sync between the devices is up to date. This means that something you tracked on one device may not be showing directly on the other device.
If you experience that issue, there is a chance that adding something to your diary on the device that is not up to date will cause the devices to sync. But we are unfortunately not able to guarantee that at the moment.