I've want to make a kind of robot that can take the temperature of clients or persons without exposing another persons. I did use an old electric car that I've found at my house and I removed all the parts I didn't need. So, all the electronic that controled this car is not there anymore. The Arduino Uno, the servos and the ultrasonic sensor are powered by a battery pack. The DC motor and the L293D chip are powered by 6 AA batteries.
The way this car works is simple. The car drive itself until the ultrasonic sensor tells tha there is less than 30 cm before the bumper of the car. Then, the small servo turns left and right. The sensor takes the distance of each sides and tells us the one with the more space and turns the wheels in this direction. If there is less than 15 cm, the car goes back during 0.5 seconds and doe the same steps than before.
I recomend that you use a infrared sensor because it isn't precise at all with the DHT11 sensor. If you had a 3D printer, you could do dedicated pieces like a case cor the UNO and a support for the ultrasonic sensor and the little servo. You could use almost any electronic car that you can find on internet for exemple. You can also steel it to your little brother or only use an old car.
To access the the temperature datas, you can add a bluetooth module or simply a red led to show that the tenperature is too hot.
P.S. Sorry for the comments in the code, they are in French.