a water mister is a great tool for plants that require a little extra moisture & there are some pretty ones out there. can usually be purchased at local garden or nursery.
a water meter is a great tool and takes the guesswork out of watering your plants. works well for larger house plants with a lot of soil. can be found at local garden or nursery.
a medicine dropper is a great for watering succulents & hard to reach terrariums. It allows for small amounts of water in a concentrated area.
take-out chopsticks are great for measuring moisture. Insert into soil- if it comes out dry, then your plant needs water. If it comes out damp, then your plant is good with water.