Human activity recognition plays an interesting and important role nowadays as there are a variety of use cases. It is utilized in health monitoring, in the development of human-computer interaction system and in security monitoring. However current methods involve usage of privacy sensitive data and impractical sensors for everyday usage. To tackle this problem, we aim to answer the research question "How to maximize the capabilities of in-mouth sensors for human activity recognition?". The main contributions of this paper are the classification of different gestures using an in-mouth device, implementation of a classifier directly onto a microcontroller and the evaluation whether the models can generalize to multiple people. To investigate this, we experimented with popular classical machine learning classifiers: Decision Tree, K-Nearest Neighbors, Support Vector Machine, Logistic Regression and Random Forest classifiers. The results shows that the F1-score of all classification problems are above 80% using the various classifiers along with different parameters.