Bandwidth Ruler for Android lets you manage your internet and tethering connections with custom boosting and throttling0
Said list is pretty rich in this case. You can set the WiFi, Mobile, and Bluetooth connection upload speed, or limit the download speed for portable WiFi hotspot and USB/Bluetooth tethering connections. The bandwidth can be automatically throttled when an arbitrary amount of data is reached. Okay, enough with the throttling and limiting! Bandwidth Ruler is a booster too. It's able to accelerate all your connections (tethered, too) through a Fast Surf feature.
With all this stuff under its belt, the app lets you create and edit data plans for your internet and tethering connections, get sound and bar notifications when thresholds are reached, make shortcuts to configure your connections, and display your connection status and IP address.
Bandwidth Ruler is free and non ad-supported. It also boasts low memory usage. There's a Pro version, though, which is updated more quickly, and supports multiple speed values for upload and download speed control.